Template-based intra mode derivation (TIMD) & decoder side intra mode derivation (DIMD)

Abstract

At least a method and an apparatus are presented for efficiently encoding or decoding video using TIMD or DIMD. For instance, the method may comprise determining that an intra mode is to be derived for predicting a current block; deriving a plurality of intra modes based on a template associated with the current block; obtaining a plurality of predictions based on the plurality of intra modes; blending the plurality of predictions to obtain the prediction block of the current block; and encoding / decoding the block based on the prediction block. In a variant, the plurality of intra modes may comprise more than 2, for instance 3 to 5 angular modes. In another variant, the plurality of intra modes comprises a first mode, a second mode and at least one additional BV mode. In yet others variant, reference lines for prediction are adapted.

Description

TEMPLATE-BASED INTRA MODE DERIVATION (TIMD) & DECODER SIDE INTRA MODE DERIVATION (DIMD)CROSS REFERENCE TO RELATED APPLICATION[1] This application claims the benefit of European Patent Application No. 23307109.1 , filed on November 30, 2023, which is incorporated herein by reference in their entirety. TECHNICAL FIELD[2] The present embodiments generally relate to a method and an apparatus for blending of intra prediction modes derived in Template-based Intra Mode Derivation TIMD or Decoderside Intra Mode Derivation DIMD process in video encoding and decoding.BACKGROUND[3] To achieve high compression efficiency, image and video coding schemes usually employ prediction and transform to leverage spatial and temporal redundancy in the video content. Generally, intra or inter prediction is used to exploit the intra or inter picture correlation, then the differences between the original block and the predicted block, often denoted as prediction errors or prediction residuals, are transformed, quantized, and entropy coded. To reconstruct the video, the compressed data are decoded by inverse processes corresponding to the entropy coding, quantization, transform, and prediction.SUMMARY[4] According to a first aspect, a method of video encoding / decoding is disclosed that comprises determining that an intra mode is to be derived for predicting a current block; deriving a plurality of intra modes based on a template associated with the current block; obtaining a plurality of predictions based on the plurality of intra modes; blending the plurality of predictions to obtain the prediction block of the current block; and encoding / decoding the block based on the prediction block.[5] According to a particular feature, the intra mode derivation is a template intra mode derivation (TIMD). According to another particular feature, the plurality of intra modes comprises more than two angular modes. According to yet another variant, one of the additional angular mode corresponds to decoder-side intra mode derivation (DIMD) mode.[6] According to another particular feature, the plurality of intra modes comprises a first mode, a second mode, a third non-angular mode and at least one additional non-angular mode obtained from the neighboring IBC / lntraTMP blocks.[7] According to yet another particular feature, an intra mode derivation is a decoder-side intra mode derivation (DIMD) mode.[8] According to another particular feature, a reference line above a reference line chosen for a previous mode is selected for obtaining the prediction with a given intra mode within anyof the intra mode derivation (ie DIMD or TIMD).[9] One or more embodiments also provide an apparatus for encoding or decoding according to the methods described herein.

[0010] One or more embodiments also provide a computer program comprising instructions which when executed by one or more processors cause the one or more processors to perform the encoding method or decoding method according to any of the embodiments described herein. One or more of the present embodiments also provide a computer readable storage medium having stored thereon instructions for encoding or decoding a video according to the methods described herein.

[0011] One or more embodiments also provide a computer readable storage medium having stored thereon video data generated according to the methods described above. One or more embodiments also provide a method and apparatus for transmitting or receiving the video data generated according to the methods described herein.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 illustrates a block diagram of a system within which aspects of the present embodiments may be implemented.

[0013] FIG. 2 illustrates a block diagram of an embodiment of a video encoder.

[0014] FIG. 3 illustrates a block diagram of an embodiment of a video decoder.

[0015] FIG. 4 illustrates a TIMD process according to prior art.

[0016] FIG. 5 illustrates a TIMD process extending the number of angular fusion modes according to a first embodiment.

[0017] FIG. 6a and 6b illustrate a TIMD process conditionally extending the number of angular fusion modes according to a first embodiment.

[0018] FIG. 7 illustrates a TIMD process extending the number of non-angular fusion modes by including other block vectors from neighboring blocks coded with intra block copy according to a second embodiment.

[0019] FIG. 8 illustrates Template-based Intra Mode Derivation (TIMD) according to an embodiment.

[0020] FIG. 9 illustrates reference line selection for TIMD mode or DIMD mode according to an embodiment.DETAILED DESCRIPTION

[0021] FIG. 1 illustrates a block diagram of an example of a system in which various aspects and embodiments can be implemented. System 100 may be embodied as a device including the various components described below and is configured to perform one or more of the aspects described in this application. Examples of such devices, include, but are not limitedto, various electronic devices such as personal computers, laptop computers, smartphones, tablet computers, digital multimedia set top boxes, digital television receivers, personal video recording systems, connected home appliances, and servers. Elements of system 100, singly or in combination, may be embodied in a single integrated circuit, multiple ICs, and / or discrete components. For example, in at least one embodiment, the processing and encoder / decoder elements of system 100 are distributed across multiple ICs and / or discrete components. In various embodiments, the system 100 is communicatively coupled to other systems, or to other electronic devices, via, for example, a communications bus or through dedicated input and / or output ports. In various embodiments, the system 100 is configured to implement one or more of the aspects described in this application.

[0022] The system 100 includes at least one processor 110 configured to execute instructions loaded therein for implementing, for example, the various aspects described in this application. Processor 110 may include embedded memory, input output interface, and various other circuitries as known in the art. The system 100 includes at least one memory 120 (e.g., a volatile memory device, and / or a non-volatile memory device). System 100 includes a storage device 140, which may include non-volatile memory and / or volatile memory, including, but not limited to, EEPROM, ROM, PROM, RAM, DRAM, SRAM, flash, magnetic disk drive, and / or optical disk drive. The storage device 140 may include an internal storage device, an attached storage device, and / or a network accessible storage device, as non-limiting examples.

[0023] System 100 includes an encoder / decoder module 130 configured, for example, to process data to provide an encoded video or decoded video, and the encoder / decoder module 130 may include its own processor and memory. The encoder / decoder module 130 represents module(s) that may be included in a device to perform the encoding and / or decoding functions. As is known, a device may include one or both of the encoding and decoding modules. Additionally, encoder / decoder module 130 may be implemented as a separate element of system 100 or may be incorporated within processor 110 as a combination of hardware and software as known to those skilled in the art.

[0024] Program code to be loaded onto processor 110 or encoder / decoder 130 to perform the various aspects described in this application may be stored in storage device 140 and subsequently loaded onto memory 120 for execution by processor 110. In accordance with various embodiments, one or more of processor 110, memory 120, storage device 140, and encoder / decoder module 130 may store one or more of various items during the performance of the processes described in this application. Such stored items may include, but are not limited to, the input video, the decoded video or portions of the decoded video, the bitstream, matrices, variables, and intermediate or final results from the processing of equations, formulas, operations, and operational logic.

[0025] In several embodiments, memory inside of the processor 110 and / or the encoder / decoder module 130 is used to store instructions and to provide working memory for processing that is needed during encoding or decoding. In other embodiments, however, a memory external to the processing device (for example, the processing device may be either the processor 110 or the encoder / decoder module 130) is used for one or more of these functions. The external memory may be the memory 120 and / or the storage device 140, for example, a dynamic volatile memory and / or a non-volatile flash memory. In several embodiments, an external non-volatile flash memory is used to store the operating system of a television. In at least one embodiment, a fast external dynamic volatile memory such as a RAM is used as working memory for video coding and decoding operations, such as for MPEG-2, HEVC, or VVC.

[0026] The input to the elements of system 100 may be provided through various input devices as indicated in block 105. Such input devices include, but are not limited to, (i) an RF portion that receives an RF signal transmitted, for example, over the air by a broadcaster, (ii) a Composite input terminal, (iii) a USB input terminal, and / or (iv) an HDMI input terminal.

[0027] In various embodiments, the input devices of block 105 have associated respective input processing elements as known in the art. For example, the RF portion may be associated with elements suitable for (i) selecting a desired frequency (also referred to as selecting a signal, or band-limiting a signal to a band of frequencies), (ii) down converting the selected signal, (iii) band-limiting again to a narrower band of frequencies to select (for example) a signal frequency band which may be referred to as a channel in certain embodiments, (iv) demodulating the down converted and band-limited signal, (v) performing error correction, and (vi) demultiplexing to select the desired stream of data packets. The RF portion of various embodiments includes one or more elements to perform these functions, for example, frequency selectors, signal selectors, band-limiters, channel selectors, filters, downconverters, demodulators, error correctors, and demultiplexers. The RF portion may include a tuner that performs various of these functions, including, for example, down converting the received signal to a lower frequency (for example, an intermediate frequency or a near-baseband frequency) or to baseband. In one set-top box embodiment, the RF portion and its associated input processing element receives an RF signal transmitted over a wired (for example, cable) medium, and performs frequency selection by filtering, down converting, and filtering again to a desired frequency band. Various embodiments rearrange the order of the above-described (and other) elements, remove some of these elements, and / or add other elements performing similar or different functions. Adding elements may include inserting elements in between existing elements, for example, inserting amplifiers and an analog-to-digital converter. In various embodiments, the RF portion includes an antenna.

[0028] Additionally, the USB and / or HDMI terminals may include respective interface processors for connecting system 100 to other electronic devices across USB and / or HDMI connections. It is to be understood that various aspects of input processing, for example, Reed-Solomon error correction, may be implemented, for example, within a separate input processing IC or within processor 110 as necessary. Similarly, aspects of USB or HDMI interface processing may be implemented within separate interface ICs or within processor 110 as necessary. The demodulated, error corrected, and demultiplexed stream is provided to various processing elements, including, for example, processor 110, and encoder / decoder 130 operating in combination with the memory and storage elements to process the datastream as necessary for presentation on an output device.

[0029] Various elements of system 100 may be provided within an integrated housing, Within the integrated housing, the various elements may be interconnected and transmit data therebetween using suitable connection arrangement 115, for example, an internal bus as known in the art, including the I2C bus, wiring, and printed circuit boards.

[0030] The system 100 includes communication interface 150 that enables communication with other devices via communication channel 190. The communication interface 150 may include, but is not limited to, a transceiver configured to transmit and to receive data over communication channel 190. The communication interface 150 may include, but is not limited to, a modem or network card and the communication channel 190 may be implemented, for example, within a wired and / or a wireless medium.

[0031] Data is streamed to the system 100, in various embodiments, using a Wi-Fi network such as IEEE 802. 11. The Wi-Fi signal of these embodiments is received over the communications channel 190 and the communications interface 150 which are adapted for Wi-Fi communications. The communications channel 190 of these embodiments is typically connected to an access point or router that provides access to outside networks including the Internet for allowing streaming applications and other over-the-top communications. Other embodiments provide streamed data to the system 100 using a set-top box that delivers the data over the HDMI connection of the input block 105. Still other embodiments provide streamed data to the system 100 using the RF connection of the input block 105.

[0032] The system 100 may provide an output signal to various output devices, including a display 165, speakers 175, and other peripheral devices 185. The other peripheral devices 185 include, in various examples of embodiments, one or more of a stand-alone DVR, a disk player, a stereo system, a lighting system, and other devices that provide a function based on the output of the system 100. In various embodiments, control signals are communicated between the system 100 and the display 165, speakers 175, or other peripheral devices 185 using signaling such as AV. Link, CEC, or other communications protocols that enable device-to-device control with or without user intervention. The output devices may be communicatively coupled to system 100 via dedicated connections through respective interfaces 160, 170, and 180. Alternatively, the output devices may be connected to system 100 using the communications channel 190 via the communications interface 150. The display 165 and speakers 175 may be integrated in a single unit with the other components of system 100 in an electronic device, for example, a television. In various embodiments, the display interface 160 includes a display driver, for example, a timing controller (T Con) chip.

[0033] The display 165 and speaker 175 may alternatively be separate from one or more of the other components, for example, if the RF portion of input 105 is part of a separate set-top box. In various embodiments in which the display 165 and speakers 175 are external components, the output signal may be provided via dedicated output connections, including, for example, HDMI ports, USB ports, or COMP outputs.

[0034] FIG. 2 illustrates an example video encoder 200, such as a VVC (Versatile Video Coding) encoder. FIG. 2 may also illustrate an encoder in which improvements are made to the VVC standard or an encoder employing technologies similar to VVC.

[0035] In the present application, the terms “reconstructed” and “decoded” may be used interchangeably, the terms “encoded” or “coded” may be used interchangeably, and the terms “image,” “picture” and “frame” may be used interchangeably. Usually, but not necessarily, the term “reconstructed” is used at the encoder side while “decoded” is used at the decoder side.

[0036] Before being encoded, the video sequence may go through pre-encoding processing (201), for example, applying a color transform to the input color picture (e.g., conversion from RGB 4:4:4 to YCbCr 4:2:0), or performing a remapping of the input picture components in order to get a signal distribution more resilient to compression (for instance using a histogram equalization of one of the color components). Metadata can be associated with the preprocessing, and attached to the bitstream.

[0037] In the encoder 200, a picture is encoded by the encoder elements as described below. The picture to be encoded is partitioned (202) and processed in units of, for example, CUs. Each unit is encoded using, for example, either an intra or inter mode. When a unit is encoded in an intra mode, it performs intra prediction (260). In an inter mode, motion estimation (275) and compensation (270) are performed. The encoder decides (205) which one of the intra mode or inter mode to use for encoding the unit, and indicates the intra / inter decision by, for example, a prediction mode flag. After prediction, prediction enhancement (285) is applied to the prediction block. Prediction residuals are calculated, for example, by subtracting (210) the predicted block from the original image block.

[0038] The prediction residuals are then transformed (225) and quantized (230). The quantized transform coefficients, as well as motion vectors and other syntax elements, areentropy coded (245) to output a bitstream. The encoder can skip the transform and apply quantization directly to the non-transformed residual signal. The encoder can bypass both transform and quantization, i.e., the residual is coded directly without the application of the transform or quantization processes.

[0039] The encoder decodes an encoded block to provide a reference for further predictions. The quantized transform coefficients are de-quantized (240) and inverse transformed (250) to decode prediction residuals. Combining (255) the decoded prediction residuals and the predicted block, an image block is reconstructed. In-loop filters (265) are applied to the reconstructed picture to perform, for example, deblocking / SAO (Sample Adaptive Offset) filtering to reduce encoding artifacts. The filtered image is stored at a reference picture buffer (280).

[0040] FIG. 3 illustrates a block diagram of an example video decoder 300. In the decoder 300, a bitstream is decoded by the decoder elements as described below. Video decoder 300 generally performs a decoding pass reciprocal to the encoding pass as described in FIG. 2. The encoder 200 also generally performs video decoding as part of encoding video data.

[0041] In particular, the input of the decoder includes a video bitstream, which can be generated by video encoder 200. The bitstream is first entropy decoded (330) to obtain transform coefficients, motion vectors, and other coded information. The picture partition information indicates how the picture is partitioned. The decoder may therefore divide (335) the picture according to the decoded picture partitioning information. The transform coefficients are de-quantized (340) and inverse transformed (350) to decode the prediction residuals. Combining (355) the decoded prediction residuals and the predicted block, an image block is reconstructed. The predicted block can be obtained (370) from intra prediction (360) or motion-compensated prediction (i.e., inter prediction) (375). After prediction, prediction enhancement (390) is applied to the prediction block. In-loop filters (365) are applied to the reconstructed image. The filtered image is stored at a reference picture buffer (380).

[0042] The decoded picture can further go through post-decoding processing (385), for example, an inverse color transform (e.g., conversion from YCbCr 4:2:0 to RGB 4:4:4) or an inverse remapping performing the inverse of the remapping process performed in the preencoding processing (201). The post-decoding processing can use metadata derived in the pre-encoding processing and signaled in the bitstream.

[0043] The present principles propose to improve the intra prediction block by modifying the blending process of intra prediction modes in TIMD or DIMD process. More specifically, TIMD fusion process in the current design is limited to using two angular modes and one non-angular mode. Including more angular modes such as ones obtained from DIMD modeadvantageously enhances TIMD fusion process. Further, other non-angular modes from neighboring intra block copy blocks may be added to the fusion process. Further, the current TIMD blending process uses two reference lines to obtain the prediction signal for blending. DIMD blending process uses only one reference line. The present principles improve this process by extending the number of reference lines in DIMD blending process and further proposes a method to carefully select the reference lines for each intra mode.

[0044] For an intra coded block, the encoder selects the best prediction mode among several modes that can be classified as: regular (regular modes may include angular modes, DC and Planar), matrix based (known as MIP) or block copy based (block copy based may include IBC and IntraTMP). It is noted that the fusion of different modes can lead to improved prediction. Recent additions to video compression technology include various industry standards, versions of the reference software and / or documentations such as Enhanced Compression Model (ECM) being developed by the JVET (Joint Video Exploration Team) group. The aim is to make further improvements to the existing VVC (Versatile Video Coding) standard. For instance, in more recent approach of video codec, TIMD and DIMD blends multiple regular modes that are deduced from a template. Recently, TIMD fusion and IntraTMP fusion are also adopted to ECM that shows some benefit of the fusion method.

[0045] Recently, some enhancements to the TIMD fusion design are proposed in ECM. For example, TIMD fusion is extended to use IBC and IntraTMP candidates obtained from neighboring blocks as potential TIMD candidates. Further to this, a third intra prediction non- angular mode can optionally be fused TIMD fusion process given that the first two intra prediction modes are different from the third intra prediction mode and the SATD cost of this non-angular mode is under a given threshold. The weights of fusion are computed based on the SATD cost. The combination of above two enhancements have also been proposed in the recent ECM and show promising results.

[0046] Knowing the advantage of fusion, this invention proposes some improvements on the existing TIMD fusion design. According to a first embodiment, the fusion angular modes may be increased to enhance the final prediction. According to a second embodiment, the fusion non-angular modes may be increased by considering neighboring block vector (BV) modes to enhance the final prediction. According to a third embodiment, to add diversity of the reference samples used to obtain the prediction, a new reference sample selection process for new angular modes is proposed. Finally, according to a fourth embodiment, DIMD merge also computes a Merged Histogram Of Gradients (MHoG) and uses the first five intra modes with highest amplitude to obtain the prediction, blend them based on the weights computed based on the amplitude of the histogram, and further blend them with the planar mode. To add diversity to the prediction samples, the reference line selection process may be modified asfor TIMD.

[0047] The following sections introduce some of the latest tools studied in ECM that may need improvements.

[0048] Decoder side intra mode derivation (PIMP)

[0049] In the latest codec experimentation, when DIMD is applied, up to five intra modes are derived from the reconstructed neighbor samples, and those five predictors are combined with the planar mode predictor with the weights derived from an Histogram Of Gradients. The division operations in weight derivation are performed utilizing the same lookup table (LUT) based integerization scheme used by the CCLM. For example, the division operation in the orientation calculationOrient = Gy / Gx(1) is computed by the following LUT-based scheme: x = Floor( Log2( Gx ) ) (2) normDiff = ( ( Gx« 4 ) » x ) & 15 (3) x +=( 3 + ( normDiff != 0 ) ? 1 : 0 ) (4)Orient = (Gy* ( DivSigTable[ normDiff ] | 8 ) + ( 1«( x-1 ) )) » x (5) whereDivSigTable

[0016] = { 0, 7, 6, 5 ,5, 4, 4, 3, 3, 2, 2, 1 , 1 , 1 , 1 , 0 } (6)

[0050] For a block of size W x H, the weight for each of the five derived modes is modified if the one the above or left histogram magnitudes is twice larger than the other one. In this case, the weights are location dependent and computed as follows:If the above histogram is twice the left, then:If the left histogram is twice the above, then:where wDimdt is the unmodified uniform weight of the DIMD, is pre-defined and set to 10.

[0051] Derived intra modes are included into the primary list of intra most probable modes (MPM), so the DIMD process is performed before the MPM list is constructed. The primary derived intra mode of a DIMD block is stored with a block and is used for MPM list construction of the neighboring blocks.

[0052] Finally, the region of neighboring reconstructed samples used for computing the histogram of gradients is modified, depending on reconstructed samples availability. The region of decoded reference samples of current WxH luma CB is extended towards the aboveright side if available, up to W additional columns. It is extended towards the bottom-left side if available, up to H additional rows.

[0053] PIMP merge mode

[0054] When using DIMD Merge, the DIMD information extracted from neighbouring blocks is used to compute the intra prediction for the current block. A new Merged Histogram of Gradients (MHoG) is computed for the current block based on the HoGs of neighbouring blocks. Only neighbouring blocks encoded with DIMD or with DIMD Merge are considered.

[0055] When a single DIMD or DIMD Merge neighbouring block is available, then its histogram of gradients is used to form the MHoG for the current block. If more than one DIMD or DIMD Merge neighbouring blocks are available, the corresponding histograms are combined by means of amplitude averaging to derive the MHoG. Up to maximum 13 blocks in the surrounding of the current block are considered to extract DIMD information.

[0056] Finally, the MHoG is used to compute intra-prediction modes and weights, as in conventional DIMD. The directional modes and their weights corresponding to the five highest amplitudes in the MHoG are selected, and the corresponding predictors are blended as in conventional DIMD.

[0057] Fusion for Template-based Intra Mode Derivation (HMD)

[0058] For each intra prediction mode in MPMs, as well as the wide-angle modes if the aboveright and / or bottom-left reference samples are available, SATD between the prediction and reconstruction samples of the template is calculated. First two intra prediction modes with the minimum SATD are selected as the TIMD modes. These two TIMD modes are fused with the weights after applying PDPC process, and such weighted intra prediction is used to code the current block. Position dependent intra prediction combination (PDPC) is included in the derivation of the TIMD modes.

[0059] The costs of the two selected modes are compared with a threshold, in the test the cost factor of 2 is applied as follows: costMode2 < 2*costMode1 . (9)If this condition is true, the fusion is applied, otherwise the only model is used.Weights of the modes are computed from their SATD costs as follows: weightl = costMode2 1 (costMode1+ costMode2) (10) weight2 = 1 - weightl (11)The division operations are conducted using the same lookup table (LUT) based integerization scheme used by the CCLM.

[0060] TIMD fusion improvements

[0061] According to an approach currently studied in ECM, TIMD with IntraTMP and IBC candidates, , it is proposed to add available IntraTMP and IBC modes of the neighboring blocks to the TIMD candidates list to predict the current block template. Up to 50 modes maybe appended to the list comprising MPM, DC mode, horizontal and vertical modes. Each prediction from IBC and IntraTMP is included in the template matching cost comparison to deduce the best two TIMD modes. If selected by the TIMD process, IntraTMP / IBC prediction is performed for the current block and the TIMD blending process is used.

[0062] According to another to prior art approach also studied in ECM, TIMD fusion process with a non-angular intra mode, a third non-angular intra prediction mode IPMNAis introduced in the TIMD fusion process.

[0063] In this approach, the non-angular intra mode IPMNA(among DC and Planar) with the lowest SATD cost is added to the TIMD fusion process if it is different from the two selected TIMD intra modes (IPM1and / PM2) and SATD(JPMNA) < k.SATDfjPM with k = 1.5.

[0064] The weights wtused during the TIMD fusion process are computed from SATD cost: sumSATD-SATDfIPMi)W;1= - - — ~ (12) 2' / .sumSATD ' ' with sumSATD = 'j3=1SATD IPMJ) (13)

[0065] The logic behind the non-angular prediction activation condition is based on already computed SATD costs. Additionally, location-dependent sample-based blending of the DIMD fusion process is re-used but the location-dependent criterion applying to amplitudes of the selected predictors is replaced by a SATD cost-based criterion. The location-dependent criterion is determined from a ratio of the normalized SATD of the selected TIMD predictors computed in ABOVE and LEFT template area, as follows:If norSATDA< - , norSATDL, locDepi = 1 (vertical) (14)Else if norSATDL< - , norSATDA, locDepi = 2 (horizontal) (15)Otherwise, locDepi = 0 (diagonal) where: locDepi is the location-dependent parameter value associated with the i-th selected TIMD mode (e.g. i belongs to [0;2]). A value of 0 indicates no location-dependency (diagonal sample-based blending), a value of 1 indicates vertical location-dependency of the i-th selected TIMD mode, a value of 2 indicates horizontal location-dependency of the i-th selected TIMD mode, norSATDAis the normalized SATD cost associated to a selected TIMD candidate and computed in ABOVE template: norSATDA= — - — (16) h-pXwcu norSATDLis the normalized SATD cost associated to a selected TIMD candidate and computed in LEFT template:i norSATDLWyX / lcu (17) with: hT, the height of the (ABOVE) template area, wT, the width of the (LEFT) template area, hcu, the height of the current Oil, wcu, the width of the current Oil.

[0066] Furthermore, block size adaptations are undertaken. The maximum weight deviation of the sample-based blending (range Af) becomes block-size dependant where bigger blocks (greater than 128 samples) have less deviations. Additionally, location-dependency is forced to 0 for small block size (width or height less than 8 samples).

[0067] Eventually, if one of the two templates is not available, the location-dependency state is set accordingly to the present template. In case of LEFT template presence only, the location-dependency is set to 2 (horizontal), otherwise in case of ABOVE template presence only, the location-dependency is set to 1 (vertical).

[0068] According to yet another prior art approach, TIMD blending process optimization is studied in ECM. For TIMD mode with blending, the first mode uses reference line I. While for the second mode, whether to use reference line I or Z+1 depends on the following conditions:- If all of the following conditions are true, I + 1 is chosen.• the current block is not ISP block,• the second mode is angular prediction mode,• the second mode does not represent non-fractional angles,- Otherwise, I is chosen.

[0069] Recently, a modification to above process has been proposed. For the second mode, the modified conditions of reference line determination are as follows (as underlined):- If all of the following conditions are true, I + 1 is chosen.• the current block is not ISP block• both the first mode and second mode are angular prediction mode• all of the following conditions are false:> absfpred Model ntrai - predModelntra2) is greater than Threshold. The value of Threshold is set to 8 or 4.> (predModelntrai - EXT HOR IPX) * (predModelntra2- EXT HOR IPX) is less than 0.> (predModelntrai - EXT VER IPX) * (predModelntra2- EXT VER IPX) is less than 0.- Otherwise, I is chosen.

[0070] This adjustment provides a small but consistent gain when evaluated over initialproposal.

[0071] Intra prediction fusion

[0072] According to another approach currently studied in ECM, an intra prediction method derives predicted samples as a weighted combination of multiple predictors generated from different reference lines. In this process, multiple intra predictors are generated and then fused by weighted averaging. The process of deriving the predictors to be used in the fusion process is described as follows:1) For angular intra prediction modes including the single mode case of TIMD and DIMD, the proposed method derives intra prediction by weighting intra predictions obtained from multiple reference lines represented as pfusion= wopline+ w1pline+1, where plineis the intra prediction from the default reference line and Pune+1is the prediction from the line above the default reference line. The weights are set as w0= 3 / 4 and w±= 1 / 4.2) For TIMD mode with blending, piineis used for the first mode (w0= i,w1= 0) and Pune+i isused for the second mode (w0= 0, 14 ! = 1).3) For DIMD mode with blending, the number of predictors selected for a weighted average is increased from 3 to 6.

[0073] Intra prediction fusion method is applied to luma blocks when angular intra mode has non-integer slope (required reference samples interpolation) and the block size is greater than 16, it is used with MRL and not applied for ISP coded blocks. In the method studied in the subtest a, PDPC is applied for the intra prediction mode using the closest to the current block reference line.

[0074] It has been demonstrated that most of the time blending of intra prediction modes derived in TIMD or DIMD process brings gain, but there still exists rooms for further improvement. The present document introduces a new method a TIMD fusion process for intra prediction that increases the number of intra prediction angular modes considered for fusion. According to additional embodiments, the reference line selection process is adapted when more angular modes are considered. Further, a reference line selection process is extended to DIMD mode which can also benefit from the added diversity of the prediction samples when performing the blending / merging.

[0075] The invention covers following main embodiments including increasing the number of intra prediction angular modes in TIMD fusion process, increasing the number of non-angular intra prediction modes (namely IBC / lntraTMP BVs) in TIMD fusion process, an adapted selection of reference line for the new intra prediction angular modes, and extending selection of reference line to DIMD mode to add diversity.

[0076] According to a generic embodiment, a method of video decoding comprises determining that an intra mode is to be derived for predicting a current block; deriving a plurality of intra modes based on a template associated with the current block; obtaining a plurality of predictions based on the plurality of intra modes; and blending the plurality of predictions to obtain the prediction block of the current block; and decoding the block based on the prediction block. According to another generic embodiment, a method of video encoding comprises determining that an intra mode is to be derived for predicting a current block; deriving a plurality of intra modes based on a template associated with the current block; obtaining a plurality of predictions based on the plurality of intra modes; and blending the plurality of predictions to obtain the prediction block of the current block; and encoding the block based on the prediction block. Such deriving of a plurality of intra modes based on a template associated with the current block may correspond to TIMD fusion process or to DIMD fusion process and various embodiments are detailed in the following.

[0077] Increasing the number of fusion angular modes in TIMD fusion process.In one embodiment, an intra mode derivation comprises a template intra mode derivation (TIMD). According to a particular feature, the plurality of intra modes comprises more than two angular modes. In a variant, the plurality of intra modes comprises 3 to 5 angular modes.

[0078] FIG. 4 illustrates a TIMD process according to prior art. In TIMD mode, the two intra prediction modes (IPM1 and IPM2) providing the minimum SATD cost are selected. In ECM, the intra prediction modes only considers regular prediction mode. Extension to use nonregular prediction modes is recently proposed in ECM as shown on FIG.4. Further, it is proposed in ECM to optionally fuse a third non-angular IPM3 when this IPM is different from the first two IPMs.

[0079] FIG. 5 illustrates a TIMD process extending the number of angular fusion modes according to a first embodiment. The first embodiment extends the concept of fusion by increasing the number of angular intra prediction modes considered for fusion. For example, the first n intra angular modes with the minimum SATD cost, that meets the threshold condition, are considered for fusion where n is 3,4 or 5. The maximum value of n can be set to 5 as an example. The threshold condition is mentioned below: costAngularModen< 2*costMode1 , where n > 1 (18)

[0080] The weights for the fusion process are computed using the SATD cost of each IPM.

[0081] As an alternative, the above threshold condition is modified as follows: costAngularModen< 2*costAngularMode1 , where n>1 (19) where costAngularModel is the SATD cost of the first angular mode. In equation (18), angular mode is added when its cost is less than twice the cost of first mode in the list (can be non-angular). In equation (19), the angular mode is added when its cost is less than twicethe cost of the first angular mode (not necessarily the first mode). Accordingly, (19) provides an alternative which is more relaxed than (18).

[0082] In a variant of this first embodiment, the number of angular modes is conditionally increased. For instance, the plurality of intra modes IPMs comprises a first mode, a second mode and at least one additional angular mode wherein a number of additional angular modes depends on the first mode and the second mode.

[0083] FIG. 6a and 6b illustrate a TIMD process conditionally extending the number of angular fusion modes according to a first embodiment. In this variant, the number of angular modes considered depends on whether the first and the second candidate are angular or non-angular. In the example of FIG. 6a, when one of the first two IPM are non-angular, an IPM3 is optionally added as an angular mode when the SATD cost threshold condition (eq. 18) is met. In another example as shown on FIG. 6b, when both the first two IPMs are non-angular, then IPM3 and IPM4 are optionally (when threshold condition is met) added as an angular mode. Accordingly, in this variant, the maximum number of TIMD modes considered for fusion are 4.

[0084] In yet another variant of this first embodiment, the additional modes correspond to DIMD derived ones. For instance, in another example, the plurality of intra modes may comprise a first mode, a second mode and at least one additional angular mode, one of the additional angular mode corresponding to decoder-side intra mode derivation (DIMD) mode. Instead of deriving further modes for TIMD, it is proposed to use the readily existing modes of DIMD. Specifically, DIMD is computed prior to TIMD in order to fill in the MPM list. The resulting DIMD modes, which are up to five, may be used as additional modes for TIMD fusion.

[0085] As a variant, the additional modes derived from DIMD are added based on the template cost. Specifically, the intra prediction mode is first mapped from 64 prediction directions to 135 prediction directions. Next, the TIMD template cost derivation process is applied to compute the SATD between the reconstructed and predicted template. The intra prediction modes that meet the below threshold condition are added as TIMD fusion candidates. costAngularModen< k*costMode1 , (20) where n > 2 and k is 2 (as a non-limiting example).

[0086] As another variation to above, a refinement of DIMD intra prediction modes is performed by adding a small offset +d to the angular mode and using the template cost to determine the best refined DIMD mode. For example, if the best DIMD intra mode is 17. A refinement process involves computing the SATD cost for intra mode 16, 17 and 18 to determine the best intra mode to be used for TIMD process. Thus, in another example, the plurality of intra modes comprises a first mode, a second mode and at least one additional angular mode, one of the additional angular mode corresponding to decoder-side intra mode derivation (DIMD) mode.

[0087] Increasing the number of non-angular fusion modes by adding IBC / lntraTMP block vector based prediction in HMD fusion process.

[0088] In one embodiment, the plurality of intra modes comprises a first mode, a second mode, a third non-angular mode and at least one additional non-angular mode obtained from the neighboring IBC / lntraTMP blocks.

[0089] FIG. 7 illustrates a TIMD process extending the number of non-angular fusion modes by adding block vectors of the neighboring IBC / lntraTmp coded blocks according to a second embodiment. In this embodiment, it is proposed to use the additional BV predictors from the neighboring blocks as potential candidates for the TIMD fusion. The BV predictors are selected based on the template cost computed between the template of the reference block and template of the current block. When the template cost is below a threshold, the BV predictor is added. For example, up to 5 BV predictors can be added to the TIMD fusion process.

[0090] Selection of reference line to compute prediction from intra prediction mode in TIMDIn a third embodiment, responsive to a criteria, a reference line above a reference line chosen for a previous angular mode is selected for obtaining the prediction with a given angular mode. In another variant, the plurality of predictions based on the plurality of intra modes are obtained, for each angular mode, by averaging a prediction based on a first neighboring reference line and a prediction based on a second reference line above the first reference line. In another variant, same principle are applied to non-angular mode wherein responsive to a criteria, a reference line above the reference line chosen for previous intra mode is used for the current additional non-angular intra mode.

[0091] When extending the number of angular modes as mentioned with the first embodiment 1 , this embodiment proposes methods to further enhance the diversity of the fusion process by optimizing the existing reference line selection process.

[0092] FIG. 8 illustrates the Template-based Intra Mode Derivation (TIMD) process according to the current design in ECM. The template of the current luminance CB of size VF x H is shown in light gray. A set of decoded reference samples of the template are shown in dark gray. All possible intra prediction directions (including the wide angle modes) are tested by computing the SATD cost between the reconstructed template (light gray 810) and predicted template using the (dark gray 820) reference samples. It is further noted that the number of reference lines above and left of the luminance CB is 2 or 4 based on the size of the block.

[0093] FIG. 9 illustrates reference line selection for TIMD mode according to the current design in ECM where only 2 reference lines above and left of the current luminance CB are considered for the TIMD mode.

[0094] Currently in ECM, the multiple reference line (MRL) list is extended providing accessto more reference lines above the current block. For TIMD, instead of full MRL, only first two reference line candidates are used. The current reference line selection process for TIMD in ECM uses the reference line I for the first intra mode and uses the reference line I or I + 1 for the second intra mode based on the criteria described above as variants of TIMD blending process optimization. Advantageously, such feature adds diversity when the two intra modes are angular and are close to each other.

[0095] The third embodiment proposes to further optimize the reference line selection process in TIMD fusion mode for the additional intra angular modes considered in the first embodiment. Specifically, for each additional angular mode considered for TIMD fusion, a reference line above the reference line chosen for the previous angular mode is selected when the said criteria are met. The rational of the said criteria is simple and is based on the closeness of the two intra angular modes. When the current and the previous angular mode is close to each other (e.g. determined by a threshold), the reference line above the reference line chosen for previous angular mode is selected to determine the prediction mode. Advantageously, this embodiment allows adding diversity for the prediction modes that are not far from each other.

[0096] As a variant, the above process may be extended by checking the distance to each previous intra angular mode. Once the angular mode is closer to any of the previous intra angular mode (e.g., determined by a threshold), the next reference line is selected. As a nonlimiting example, when the additional angular modes added to TIMD fusion is the third mode, the reference line selection process may be modified as follows:- If all of the following conditions are true, I + 2 is chosen:• the current block is not ISP block,• the first mode, second and third mode are angular prediction mode,• second mode uses I + 1 reference line,• all of the following conditions are false: abs(predModelntra2 - predModelntra3) is greater than Threshold. The value of Threshold is set to 8 or 4. (predModelntra2- EXT_HOR_IDX) * (predModelntra3- EXT_HOR_IDX) is less than 0. (predModelntra2- EXT_VER_IDX) * (predModelntra3- EXT_VER_IDX) is less than 0.- Otherwise, I + 1 is chosen if following conditions are true:• second mode uses I reference line,• all of the following conditions are false, abs(predModelntrai - predModelntra3) is greater than Threshold. The value of Threshold is set to 8 or 4. (predModelntrai - EXT_HOR_IDX) * (predModelntra3- EXT_HOR_IDX) is less than 0. (predModelntrai - EXT_VER_IDX) * (predModelntra3- EXT_VER_IDX) is less than 0.- Otherwise, I is chosen.

[0097] Similarly, the above process is repeated for jthintra angular mode to one of the / reference lines.

[0098] In a variant of the third embodiment, reference line selection process may also be adapted when first two TIMD modes contains non-angular modes. As a variant, an additional intra angular mode is added as third mode and use I + 1 reference line based on the following criteria:• current block is not ISP block,• either first or second mode is a non-angular mode,• at least one of the first two modes is an angular mode,• all following conditions are false: abs (predModelntraanguiar - predModelntra3) greater than threshold. Threshold value is set to 4 or 8, (predMod less than(predModelntraanguiar- EXT_VER_IDX) *(predModelntra3 - EXT_VER_IDX) is less than 0,Otherwise, I is used

[0099] Another variant is when an additional intra prediction angular mode is added as the fourth mode in the fusion process and the I + 1 reference line are used based on the following criteria:• current block is not ISP block,• both first and second mode are non-angular modes,• the third mode added is an angular mode,• all following conditions are false: abs (predModelntra3- predModelntra^ greater than threshold. Threshold value is set to 4 or 8, (predModelntra3- EXT_HOR_IDX) *(predModelntra3 - EXT_HOR_IDX) is less than 0, (predModelntra3- EXT_VER_IDX) *(predModelntra3 - EXT_VER_IDX) is less than 0,Otherwise, I is used.

[0100] In another variant of the third embodiment, reference line selection process may also be adapted for TIMD fusion process with a non-angular intra mode.

[0101] As mentioned for TIMD fusion process with a non-angular intra mode, it is proposed to optionally fuse a third intra mode as a non-angular mode. In this scenario, the reference line I + 1 may be used for this mode when following condition is met:• the third non-angular mode is either DC or Planar,• current block is not ISP block,• when first two modes have used I reference line (this adds diversity),- Otherwise, I is used as the reference line.

[0102] As a variant to above, when the first two modes are non-angular (but not IBC or IntraTMP), then to add diversity, use I + 1 reference line for the second mode when following condition is met:• current block is not ISP block• both first and second mode are non-angular, and at least one of them is not IBC orIntraTMP mode- Otherwise, I is used as the reference line.

[0103] In yet another variant of the third embodiment, fusion of prediction may be obtained from multiple reference lines.

[0104] TIMD fusion process blends the prediction samples from two intra prediction modes. For first mode, reference line I is used. For second mode, I + 1 is selected in certain cases. In this variant, it is proposed to compute prediction using both I and I + 1 reference lines. The two predictions are then averaged. Finally, this averaged prediction is fused with the prediction using first mode based on the computed weights.

[0105] In yet another variant, the averaging of prediction samples using I and I + 1 is done for non-angular DC and planar mode only.

[0106] Selection of reference lines to compute prediction from intra prediction modes in PIMP mode.

[0107] In another embodiment, when the intra mode derivation comprises a decoder-side intra mode derivation (DIMD) mode, responsive to a criteria, a reference line above a reference line chosen for a previous angular mode is selected for obtaining the prediction with a given angular mode. Further, the plurality of predictions based on the plurality of intra modes in DIMD may be obtained, for each angular mode, by averaging a prediction based on a first neighboring reference line and a prediction based on a second reference line above the first reference line.

[0108] DIMD mode and DIMD merge mode first computes a HoG. Then, it selects the five prediction modes with highest amplitude in the histogram HoG and blends them together using weights computed from the same HoG. Finally, blending is done with a planar mode.

[0109] Same reference line is used for all five prediction modes to construct a prediction block.To add diversity, reference line selection process for intra angular modes described in the previous section for TIMD is extended to DIMD mode and DIMD merge mode.

[0110] As a variant, different reference lines are used to construct multiple prediction signal that are then blended by simple averaging. Further merging of the averaged prediction signal is done as usually done in DIMD.

[0111] Various methods are described herein, and each of the methods comprises one or more steps or actions for achieving the described method. Unless a specific order of steps or actions is required for proper operation of the method, the order and / or use of specific steps and / or actions may be modified or combined. Additionally, terms such as “first”, “second”, etc. may be used in various embodiments to modify an element, component, step, operation, etc., for example, a “first decoding” and a “second decoding”. Use of such terms does not imply an ordering to the modified operations unless specifically required. So, in this example, the first decoding need not be performed before the second decoding, and may occur, for example, before, during, or in an overlapping time period with the second decoding.

[0112] Various methods and other aspects described in this application can be used to modify modules, for example, the motion compensation module (270) of a video encoder 200 as shown in FIG. 2. Moreover, the present aspects are not limited to ECM and VVC, and can be applied, for example, to other standards and recommendations, and extensions of any such standards and recommendations. Unless indicated otherwise, or technically precluded, the aspects described in this application can be used individually or in combination.

[0113] Various numeric values are used in the present application. The specific values are for example purposes and the aspects described are not limited to these specific values.

[0114] Various implementations involve decoding. “Decoding,” as used in this application, may encompass all or part of the processes performed, for example, on a received encoded sequence in order to produce a final output suitable for display. In various embodiments, such processes include one or more of the processes typically performed by a decoder, for example, entropy decoding, inverse quantization, inverse transformation, and differential decoding. Whether the phrase “decoding process” is intended to refer specifically to a subset of operations or generally to the broader decoding process will be clear based on the context of the specific descriptions and is believed to be well understood by those skilled in the art.

[0115] Various implementations involve encoding. In an analogous way to the above discussion about “decoding”, “encoding” as used in this application may encompass all or part of the processes performed, for example, on an input video sequence in order to produce an encoded bitstream.

[0116] Note that the syntax elements as used herein are descriptive terms. As such, they do not preclude the use of other syntax element names.

[0117] The implementations and aspects described herein may be implemented in, for example, a method or a process, an apparatus, a software program, a data stream, or a signal. Even if only discussed in the context of a single form of implementation (for example, discussed only as a method), the implementation of features discussed may also be implemented in other forms (for example, an apparatus or program). An apparatus may be implemented in, for example, appropriate hardware, software, and firmware. The methods may be implemented in, for example, an apparatus, for example, a processor, which refers to processing devices in general, including, for example, a computer, a microprocessor, an integrated circuit, or a programmable logic device. Processors also include communication devices, for example, computers, cell phones, portable / personal digital assistants (“PDAs”), and other devices that facilitate communication of information between end-users.

[0118] Reference to “one embodiment” or “an embodiment” or “one implementation” or “an implementation”, as well as other variations thereof, means that a particular feature, structure, characteristic, and so forth described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrase “in one embodiment” or “in an embodiment” or “in one implementation” or “in an implementation”, as well any other variations, appearing in various places throughout this application are not necessarily all referring to the same embodiment.

[0119] Additionally, this application may refer to “determining” various pieces of information. Determining the information may include one or more of, for example, estimating the information, calculating the information, predicting the information, or retrieving the information from memory.

[0120] Further, this application may refer to “accessing” various pieces of information. Accessing the information may include one or more of, for example, receiving the information, retrieving the information (for example, from memory), storing the information, moving the information, copying the information, calculating the information, determining the information, predicting the information, or estimating the information.

[0121] Additionally, this application may refer to “receiving” various pieces of information. Receiving is, as with “accessing”, intended to be a broad term. Receiving the information may include one or more of, for example, accessing the information, or retrieving the information (for example, from memory). Further, “receiving” is typically involved, in one way or another, during operations, for example, storing the information, processing the information, transmitting the information, moving the information, copying the information, erasing the information, calculating the information, determining the information, predicting the information, or estimating the information.

[0122] It is to be appreciated that the use of any of the following 7”, “and / or”, and “at least oneof”, for example, in the cases of “A / B”, “A and / or B” and “at least one of A and B”, is intended to encompass the selection of the first listed option (A) only, or the selection of the second listed option (B) only, or the selection of both options (A and B). As a further example, in the cases of “A, B, and / or C” and “at least one of A, B, and C”, such phrasing is intended to encompass the selection of the first listed option (A) only, or the selection of the second listed option (B) only, or the selection of the third listed option (C) only, or the selection of the first and the second listed options (A and B) only, or the selection of the first and third listed options (A and C) only, or the selection of the second and third listed options (B and C) only, or the selection of all three options (A and B and C). This may be extended, as is clear to one of ordinary skill in this and related arts, for as many items as are listed.

[0123] Also, as used herein, the word “signal” refers to, among other things, indicating something to a corresponding decoder. For example, in certain embodiments the encoder signals a quantization matrix for de-quantization. In this way, in an embodiment the same parameter is used at both the encoder side and the decoder side. Thus, for example, an encoder can transmit (explicit signaling) a particular parameter to the decoder so that the decoder can use the same particular parameter. Conversely, if the decoder already has the particular parameter as well as others, then signaling can be used without transmitting (implicit signaling) to simply allow the decoder to know and select the particular parameter. By avoiding transmission of any actual functions, a bit savings is realized in various embodiments. It is to be appreciated that signaling can be accomplished in a variety of ways. For example, one or more syntax elements, flags, and so forth are used to signal information to a corresponding decoder in various embodiments. While the preceding relates to the verb form of the word “signal”, the word “signal” can also be used herein as a noun.

[0124] As will be evident to one of ordinary skill in the art, implementations may produce a variety of signals formatted to carry information that may be, for example, stored or transmitted. The information may include, for example, instructions for performing a method, or data produced by one of the described implementations. For example, a signal may be formatted to carry the bitstream of a described embodiment. Such a signal may be formatted, for example, as an electromagnetic wave (for example, using a radio frequency portion of spectrum) or as a baseband signal. The formatting may include, for example, encoding a data stream and modulating a carrier with the encoded data stream. The information that the signal carries may be, for example, analog or digital information. The signal may be transmitted over a variety of different wired or wireless links, as is known. The signal may be stored on a processor-readable medium.

[0125] We describe a number of embodiments. Features of these embodiments can be provided alone or in any combination, across various claim categories and types. Further,embodiments can include one or more of the following features, devices, or aspects, alone or in any combination, across various claim categories and types:

Claims

CLAIMS1. A method of video decoding, comprising: determining that an intra mode is to be derived for predicting a current block; deriving a plurality of intra modes based on a template associated with the current block; obtaining a plurality of predictions based on the plurality of intra modes; blending the plurality of predictions to obtain the prediction block of the current block; and decoding the block based on the prediction block.

2. The method of claim 1 , wherein an intra mode derivation comprises a template intra mode derivation (TIMD).

3. The method of claim 2, wherein the plurality of intra modes comprises more than two angular modes.

4. The method of claim 2, wherein the plurality of intra modes comprises 3 to 5 angular modes.

5. The method of claim 2, wherein the plurality of intra modes comprises a first mode, a second mode and at least one additional angular mode wherein a number of additional angular modes depends on the first mode and the second mode.

6. The method of claim 2, wherein the plurality of intra modes comprises a first mode, a second mode and at least one additional angular mode, one of the additional angular mode corresponding to decoder-side intra mode derivation (DIMD) mode.

7. The method of claim 2, wherein the plurality of intra modes comprises a first mode, a second mode and at least one additional angular mode, one of the additional angular mode corresponding to decoder-side intra mode derivation (DIMD) mode and one of the additional angular mode corresponding to decoder-side intra mode derivation (DIMD) mode with an offset.

8. The method of claim 2, wherein the plurality of intra modes comprises a first mode, a second mode, a third non-angular mode and at least one additional non-angular mode obtained from the neighboring IBC / lntraTMP blocks.

9. The method of claim 3, wherein, responsive to a criteria, a reference line above a reference line chosen for a previous angular mode is selected for obtaining the prediction with a given angular mode.

10. The method of claim 3, wherein, obtaining a plurality of predictions based on the plurality of intra modes comprises, for each angular mode, averaging a prediction based on a first neighboring reference line and a prediction based on a second reference line above the first reference line.

11. The method of claim 1 , wherein an intra mode derivation comprises a decoder-side intra mode derivation (DIMD) mode, and wherein, responsive to a criteria, a reference line above a reference line chosen for a previous angular mode is selected for obtaining the prediction with a given angular mode.

12. The method of claim 1 , wherein an intra mode derivation comprises a decoder-side intra mode derivation (DIMD) mode, and wherein, obtaining a plurality of predictions based on the plurality of intra modes comprises, for each angular mode, averaging a prediction based on a first neighboring reference line and a prediction based on a second reference line above the first reference line.

13. The method of claim 8, wherein, responsive to a criteria, a reference line above the reference line chosen for previous intra mode is used for the current additional non-angular intra mode.

14. A method of video encoding, comprising: determining that an intra mode is to be derived for predicting a current block; deriving a plurality of intra modes based on a template associated with the current block; obtaining a plurality of predictions based on the plurality of intra modes; blending the plurality of predictions to obtain the prediction block of the current block; and decoding the block based on the prediction block.

15. The method of claim 14, wherein an intra mode derivation comprises a template intra mode derivation (TIMD).

16. The method of claim 15, wherein the plurality of intra modes comprises more than two angular modes.

17. The method of claim 15, wherein the plurality of intra modes comprises 3 to 5 angular modes.

18. The method of claim 15, wherein the plurality of intra modes comprises a first mode, a second mode and at least one additional angular mode wherein a number of additional angular modes depends on the first mode and the second mode.

19. The method of claim 15, wherein the plurality of intra modes comprises a first mode, a second mode and at least one additional angular mode, one of the additional angular mode corresponding to decoder-side intra mode derivation (DIMD) mode.

20. The method of claim 15, wherein the plurality of intra modes comprises a first mode, a second mode and at least one additional angular mode, one of the additional angular mode corresponding to decoder-side intra mode derivation (DIMD) mode and one of the additional angular mode corresponding to decoder-side intra mode derivation (DIMD) mode with an offset.21 The method of claim 15, wherein the plurality of intra modes comprises a first mode, a second mode, a third non-angular mode and at least one additional non-angular mode obtained from the neighboring IBC / lntraTMP blocks.

22. The method of claim 16, wherein, responsive to a criteria, a reference line above a reference line chosen for a previous angular mode is selected for obtaining the prediction with a given angular mode.

23. The device of claim 16, wherein, obtaining a plurality of predictions based on the plurality of intra modes comprises, for each angular mode, averaging a prediction based on a first neighboring reference line and a prediction based on a second reference line above the first reference line.

24. The method of claim 14, wherein an intra mode derivation comprises a decoder-side intra mode derivation (DIMD) mode, and wherein, responsive to a criteria, a reference line above a reference line chosen for a previous angular mode is selected for obtaining the prediction with a given angular mode.

25. The method of claim 14, wherein an intra mode derivation comprises a decoder-side intra mode derivation (DIMD) mode, and wherein, obtaining a plurality of predictions based on the plurality of intra modes comprises, for each angular mode, averaging a prediction based on a first neighboring reference line and a prediction based on a second reference line above the first reference line.

26. The method of claim 21 , wherein, responsive to a criteria, a reference line above the reference line chosen for previous intra mode is used for the current additional non-angular intra mode.

27. An apparatus, comprising one or more processors, wherein said one or more processors are configured to perform the method of any of claims 1-26.

28. A signal comprising video data, formed by performing the method of any one of claims14-26.

29. A computer readable storage medium having stored thereon instructions for video decoding or encoding according to the method of any one of claims 1-26.

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