Adaptive scaling filter selection in dynamic resolution coding

Abstract

A mechanism for processing video data is disclosed. The mechanism includes determining to select one or more adaptive scaling filters. A conversion is performed between a visual media data and a bitstream based on the adaptive scaling filters.

Description

P24092451501WO1; G25N20990W (4824-70001)Adaptive Scaling Filter Selection In Dynamic Resolution CodingCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This patent application claims the benefit of U.S. Provisional Patent Application No. 63 / 694,021 filed on September 12, 2024. which is hereby incorporated by reference in its entirety.TECHNICAL FIELD

[0002] The present disclosure relates to generation, storage, and consumption of digital audio video media information in a file format.BACKGROUND

[0003] Digital video accounts for the largest bandwidth used on the Internet and other digital communication networks. As the number of connected user devices capable of receiving and displaying video increases, the bandwidth demand for digital video usage is likely to continue to grow.SUMMARY

[0004] A first aspect relates to a method for processing media data, comprising:

[0005] determining to select one or more adaptive scaling filters from a predefined list of candidates for a level or to generate an online-trained adaptive filter; and performing a conversion between a visual media data and a bitstream based on the one or more adaptive scaling filters selected or online-trained adaptive filter generated.

[0006] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the level comprises a frame, a partition, a tile, a coding tree unit (CTU). a block, or a sub-block.

[0007] Optionally, in any of the preceding aspects, another implementation of the aspect provides preparing the pre-defined list of candidates.

[0008] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the pre-defined list of candidates comprises motion compensation filters at sub-pel positions, pre-trained reference picture resample (RPR) filters, bicubic filters, and Lanczos filters.

[0009] Optionally, in any of the preceding aspects, another implementation of the aspect provides applying a criterion to compare and select the one or more scaling filters from the predefined list of candidates.

[0010] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the criterion comprises a rate-distortion cost.

[0011] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the rate-distortion cost combines scaling distortion and corresponding signaling bits.P24092451501WO1; G25N20990W (4824-70001)

[0012] Optionally, in any of the preceding aspects, another implementation of the aspect provides that an adaptive upscaling filter is determined by an adaptive upscaling filter module.

[0013] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a filter providing a lowest cost is selected during rate-distortion optimization (RDO).

[0014] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a filter providing a lowest distortion is selected when quality is prioritized and when overhead from signaling bits remains within a specific limit.

[0015] Optionally, in any of the preceding aspects, another implementation of the aspect provides comparing rescaling distortions to determine a downscaling filter.

[0016] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the rescaling distortions are obtained after a current frame has been downscaled with each filter candidate and upscaling the current frame with an upscaling filter.

[0017] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the upscaling filter is determined by an upscaling filter selection mechanism.

[0018] Optionally, in any of the preceding aspects, another implementation of the aspect provides analyzing several frames in a video sequence.

[0019] Optionally, in any of the preceding aspects, another implementation of the aspect provides that features of the video sequence and an offline-trained classifier are used to determine a downscaling filter for the video sequence.

[0020] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the bitstream includes an index of the one or more scaling filters selected.

[0021] Optionally, in any of the preceding aspects, another implementation of the aspect provides sorting frequencies of the one or more scaling filters selected.

[0022] Optionally, in any of the preceding aspects, another implementation of the aspect provides that filter indices of the frequencies are coded in increasing code lengths as frequencies decrease.

[0023] Optionally, in any of the preceding aspects, another implementation of the aspect provides entropy encoding the filter indices.

[0024] Optionally, in any of the preceding aspects, another implementation of the aspect provides entropy encoding the filter indices using Huffman codes.

[0025] Optionally, in any of the preceding aspects, another implementation of the aspect provides that signal codes of filter indices are included in the bitstream.

[0026] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the signal codes instruct a decoder to apply the one or more adaptive scaling filters selected.P24092451501WO1; G25N20990W (4824-70001)

[0027] Optionally, in any of the preceding aspects, another implementation of the aspect provides that signal codes of filter indices are included in supplemental information.

[0028] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the signal codes permit a decoder to determine whether or not to apply the one or more adaptive scaling filters selected.

[0029] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the online-trained adaptive filter is encoded in the bitstream.

[0030] Optionally, in any of the preceding aspects, another implementation of the aspect provides generating predictions of the online-trained adaptive filter based on at least one of previously encoded frames and previously decoded frames.

[0031] Optionally, in any of the preceding aspects, another implementation of the aspect provides that differences between the predictions of the online-trained adaptive filter and coefficients of the online-trained adaptive filter are entropy coded.

[0032] Optionally, in any of the preceding aspects, another implementation of the aspect provides collecting coefficients of the online-trained adaptive filter.

[0033] Optionally, in any of the preceding aspects, another implementation of the aspect provides performing lossy reconstruction of the online-trained adaptive filter using vector quantizers trained offline.

[0034] Optionally, in any of the preceding aspects, another implementation of the aspect provides comparing the online-trained adaptive filter with filter candidates in the predefined list of candidates.

[0035] Optionally, in any of the preceding aspects, another implementation of the aspect provides selecting one of the filter candidates with a best performance.

[0036] Optionally, in any of the preceding aspects, another implementation of the aspect provides computing the rate distortion (RD) cost of the online-trained adaptive filter and comparing the RD cost of the online-trained adaptive filter with the filter candidates in the predefined list of candidates.

[0037] Optionally, in any of the preceding aspects, another implementation of the aspect provides processing index signal bits along with corresponding information when the online-trained adaptive filter is selected.

[0038] Optionally, in any of the preceding aspects, another implementation of the aspect provides transmitting the processing index signal bits and the corresponding information.

[0039] Optionally, in any of the preceding aspects, another implementation of the aspect provides that coefficients for the one or more adaptive scaling filters or the online-trained adaptive filter comprise Wiener coefficients.P24092451501WO1; G25N20990W (4824-70001)

[0040] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the Wiener coefficients at two sub-pel positions that are symmetric about 1 / 2 exhibit symmetry.

[0041] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the coefficients at the 3 / 4 sub-pel position are c3. c2. cl, and cO when the coefficients at the 1 / 4 sub-pel position are cO, cl. c2. and c3, respectively.

[0042] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the coefficients at the 1 / 2 sub-pel position are symmetric.

[0043] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the coefficients comprise cO, cl, cl, cO.

[0044] Optionally, in any of the preceding aspects, another implementation of the aspect provides that Wiener filters for only half of the sub-pel positions are compressed and transmitted.

[0045] Optionally, in any of the preceding aspects, another implementation of the aspect provides that 15 sub-pel positions are used for a luma channel and 31 sub-pel positions are used for each chroma channel when the scaling precision is 1 / 16 pixel.

[0046] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a maximum of 8 sets of the Wiener coefficients for the luma channel and 16 sets of the Wiener coefficients for each chroma chamrcl arc included in the bitstream.

[0047] Optionally, in any of the preceding aspects, another implementation of the aspect provides that coefficients of a reduced set of the Weiner filters are included in the bitstream.

[0048] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the visual media data includes a video unit, and wherein the video unit comprises a sequence, picture, subpicture, slice, tile, coding tree unit (CTU), CTU row, groups of CTU, coding unit (CU), prediction unit (PU), transform unit (TU). coding tree block (CTB), coding block (CB), prediction block (PB), transform block (TB), or any other region that contains more than one luma or chroma sample or pixel.

[0049] Optionally, in any of the preceding aspects, another implementation of the aspect provides that whether to and / or how to apply one or more of the methods is indicated in the bitstream at sequence level, group of pictures level, picture level, slice level, or tile group level, or in a sequence header, picture header, sequence parameter set (SPS), video parameter set (VPS), decoding parameter set (DPS), decoding capability information (DCI), picture parameter set (PPS), Adaptation Parameter Set (APS), slice header, or tile group header.

[0050] Optionally, in any of the preceding aspects, another implementation of the aspect provides that whether to or how to apply one or more of the methods is dependent on: a message included in a DPS, SPS, VPS, PPS, APS, picture header, slice header, tile group header, CTU, CU, CTU row, group of CTUs, TU, PUP2409245150IWO1; G25N20990W (4824-70001) block, or video coding unit: a position of CU, PU, TU, block, or video coding unit; a block dimension of current block or a block dimension of neighbouring blocks; a block shape of current block or a block shape of neighbouring blocks; a coded mode of a block including intra block copy (IBC) mode, non-IBC inter mode, or non-IBC subblock mode; an indication of a colour format; a coding tree structure; a slice type, tile group type, or picture type; a colour component only applied on chroma components or luma components; a temporal layer identifier (ID); or a profile, level, or tier.

[0051] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a syntax element in the bitstream is binarized as a flag, a fixed length code, an EG(x) code, a unary code, a truncated unary code, or a truncated binary code, and wherein the syntax clement is signed or unsigned.

[0052] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a syntax element in the bitstream is coded with at least one context model or is bypass coded.

[0053] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a syntax element is signaled in a conditional way.

[0054] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the syntax element is in the bitstream only when the corresponding function is applicable.

[0055] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the syntax element is in the bitstream only when dimensions including width or height of a block satisfy a condition.

[0056] Optionally, in any of the preceding aspects, another implementation of the aspect provides that a syntax element is included in the bitstream at a block level, sequence level, group of pictures level, picture level, slice level, or tile group level, or in one or more coding structures comprising a coding tree unit (CTU), coding unit (CU), transform unit (TU), prediction unit (PU), coding tree block (CTB), coding block (CB), transform block (TB), prediction block (PB), sequence header, picture header, sequence parameter set (SPS), video parameter set (VPS), dependency parameter set (DPS), decoding capability information (DCI), picture parameter set (PPS), adaptation parameter set (APS), slice header, or tile group header.

[0057] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the method is combined with another coding tool including affine, Multi Transform Selection (MTS), Low- Frequency Non-Separable Transform (LFNST), merge mode with motion vector difference (MMVD), Matrix-based Intra Prediction (MIP), intra sub-partitions (ISP), Cross-Component Linear Model (CCLM), convolutional cross-component model (CCCM), Symmetrical motion vector difference (SMVD). Bidirectional optical flow (BDOF), decoder-side motion vector refinement (DMVR), history-based motion vector prediction (HMVP), Template Matching, intra block copy (IBC), or Palette.P24092451501WO1; G25N20990W (4824-70001)

[0058] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the method is excluded from being used with another coding tool including affine, MTS, LFNST, MMVD, MIP, ISP, CCLM, CCCM, SMVD, BDOF, DMVR, HMVP, Template Matching, IBC, or Palette.

[0059] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the excluded coding tool is disabled implicitly without signaling when the method is used.

[0060] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the method is disabled implicitly without signaling when the excluded coding tool is used.

[0061] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the conversion includes encoding the visual media data into the bitstream.

[0062] Optionally, in any of the preceding aspects, another implementation of the aspect provides that the conversion includes decoding the visual media data from the bitstream.

[0063] A second aspect relates to 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 the method of any of the disclosed aspects.

[0064] A third aspect relates to a non-transitory computer readable medium comprising a computer program product for use by a video coding device, the computer program product comprising computer executable instructions stored on the non-transitory computer readable medium such that when executed by a processor cause the video coding device to perform the method of any of the disclosed aspects.

[0065] A fourth aspect relates to a non-transitory computer-readable recording medium storing a bitstream of a video which is generated by a method performed by a video processing apparatus, wherein the method comprises: determining to select one or more adaptive scaling filters from a predefined list of candidates for a level or to generate an online-trained adaptive filter; and generating a bitstream based on the determination.

[0066] A fifth aspect relates to a method for storing bitstream of a video comprising: determining to select one or more adaptive scaling filters from a predefined list of candidates for a level or to generate an online-trained adaptive filter; generating a bitstream based on the determination; and storing the bitstream in a non-transitory computer-readable recording medium.

[0067] A sixth aspect relates to a method, apparatus, or system described in the present disclosure.

[0068] For the purpose of clarity, any one of the foregoing embodiments may be combined with any one or more of the other foregoing embodiments to create a new embodiment within the scope of the present disclosure.

[0069] These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims.P24092451501WO1; G25N20990W (4824-70001)BRIEF DESCRIPTION OF THE DRAWINGS

[0070] For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts.

[0071] FIG. 1 illustrates an example pipeline of a reference picture resample (RPR) scheme in a Versatile Video Coding (VVC) Test Model (VTM) encoder.

[0072] FIG. 2 illustrates an example pipeline of RPR frame decoding in the WC Test Model.

[0073] FIG. 3 is a block diagram showing an example video processing system.

[0074] FIG. 4 is a block diagram of an example video processing apparatus.

[0075] FIG. 5 is a flowchart for an example method of video processing.

[0076] FIG. 6 is a block diagram that illustrates an example video coding system.

[0077] FIG. 7 is a block diagram that illustrates an example encoder.

[0078] FIG. 8 is a block diagram that illustrates an example decoder.

[0079] FIG. 9 is a schematic diagram of an example encoder.DETAILED DESCRIPTION

[0080] It should be understood at the outset that although an illustrative implementation of one or more embodiments are provided below, the disclosed systems and / or methods may be implemented using any number of techniques, whether currently known or yet to be developed. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated below, including the exemplary designs and implementations illustrated and described herein, but may be modified within the scope of the appended claims along with their full scope of equivalents.

[0081] Section headings are used in the present disclosure for ease of understanding and do not limit the applicability of techniques and embodiments disclosed in each section only to that section. Furthermore,H.266 terminology is used in some description only for ease of understanding and not for limiting scope of the disclosed techniques. As such, the techniques described herein are applicable to other video codec protocols and designs also.I. Initial discussion

[0082] This disclosure is related to techniques for frame scaling in video coding. Specifically, the scaling techniques include selecting filters adaptive to each frame, encoding the filter information, and utilizing scaled frames as reference frames. These techniques are designed and implemented to improve the quality and coding efficiency in the reference picture resampling (RPR) scheme in H.266 / versatile video coding (WC). To a larger extent, they can also be applied to other video coding standards, such as H.264 / Advanced Video Coding (AVC) and H.265 / High Efficiency Video Coding (HEVC) to which dynamic resolution coding canP24092451501WO1; G25N20990W (4824-70001) be applied. Scalable High Efficient Video Coding (SHVC), Alliance for Open Media (AOM) AOMedia Video 1 (AVI) and AOM Video Model (AVM) AOMedia Video 2 (AV2) which also support RPR, and are potentially applicable to other video coding standards or codecs, such as the successor of H.266 / WC, as long as frame scaling is performed.2. Further discussion

[0083] Frame resolution changes during encoding have garnered attention due to their adaptability to varying network conditions, their suitability for spatial scalability, and the coding efficiency achieved through reduced side information. When a streaming network suddenly becomes congested, maintaining the original encoding resolution and bitrate can cause playback issues. By encoding at a lower resolution, the bitrate decreases to accommodate bandwidth limitations, ensuring smooth playback. Additionally, in scenarios like scene transitions or speaker changes in video conferences, resolution often fluctuates. Lower resolution encoding can also improve compression efficiency by reducing the need for side information, thus allowing more bits for residual data at a constant bitrate. In high-resolution encoding, redundant side information can occur due to the strict limits on Coding Tree Unit (CTU) size, particularly in uniform regions that are overpartitioned. Lowering the resolution ensures the frame size better fits the maximum CTU size, balancing the side and residual information more effectively.

[0084] Dynamic resolution encoding [1.2], hybrid resolution switching [3] and adaptive resolution controlling [4] are among the terms use to refer to this strategy. However, other works are limited by the inability of encoders (e.g., AVC Joint Test Model (JM), HEVC Test Model (HM), Fraunhofer Versatile Video Encoder (WEnC)) to support intcr-framc motion compensation between frames of different resolutions. Consequently, researchers could only switch resolutions during encoding at intra random access points (IRAP) or instantaneous decoder refresh (IDR) frames within closed Group Of Pictures (GOP) structures. The emergence of the latest video coding standard, H.266 / VVC [5], with reference picture resampling (RPR) techniques, alleviated these limitations by enabling motion compensation from reference frames of different resolutions. During motion estimation, when the resolutions of the current and reference frames differ, the reference frames arc scaled to match the current frame's resolution prior to motion search. On the decoder side, when motion compensation is required from a reference frame of different resolution, rescaling occurs at the block level [6], The scaling-on-demand approach gives RPR the flexibility to switch to the desired resolution at any point within an open or closed GOP, rather than being limited to IRAP frames at closed GOP boundaries. This mitigates bitrate spikes at resolution-switching points observed in other coding standards.

[0085] The choice of scaling method is a major issue for the performance of adaptive resolution encoding or RPR. The rescaling distortion, after the original frame being decimated to a fraction as small as 2 / 3 or 1 / 2 of the frame’s size then upscaled, affects both frame quality and coding efficiency. When the rescaling distortion is low, encoding in lower resolution enables better coding efficiency by reducing the sideP24092451501WO1; G25N20990W (4824-70001) information while retaining details [7], However, if the chosen downscaling or upscaling method introduces significant distortion, the optimal lower resolution may not be selected. Additionally, if an RPR frame with rescaling distortion is used as a reference [8], this distortion propagates to subsequent frames, degrading overall coding performance.3. Technical problems solved by disclosed technical solutions

[0086] The performance of scaling methods significantly impacts both display quality and coding efficiency in adaptive resolution encoding and RPR scenarios. However, the practical implementation still faces challenges that include, but are not limited to, the following issues:• No universal scaling method consistently performs well across all frames due to the diversity of frame content.• Complexity of scaling algorithms is limited by the constraints on codec complexity. High- complexity algorithms, such as artificial intelligence (Al)-based image resizing or super-resolution techniques, are not accepted in current video coding standards.• The information about the adaptive scaling approach, for example Wiener filter, needs to be efficiently encoded and transmitted, so as not to increase the filter information signaling overhead too much.

[0087] Specifically, if a Wiener filter is used as the adaptive approach, an improved compression scheme on the coefficients should be designed, in order to fit for the random access applications. While the Wiener scaling filter can adapt to frame statistics, as demonstrated in [8], transmitting the filter coefficients to the decoder increases transmission overhead. Wiener filters perfonn well in low-delay tests where coefficients are predicted and encoded from the nearest previous frame without significant variation. However, in random access scenarios with higher coding efficiency, Wiener coefficients cannot be easily predicted from the nearest frames in that the frames are not encoded in display order, and the improvement in rescaling quality may not compensate for the large overhead associated with coefficient transmission. Thus, a low-complexity adaptive scaling method with an efficient compression technique is beneficial.4. Exemplary Solutions

[0088] The following detailed solutions illustrate general concepts and should not be interpreted narrowly. These examples may be combined in any manner.

[0089] FIG. 1 illustrates an example pipeline of a RPR scheme in a Versatile Video Coding (VVC) Test Model encoder.

[0090] An example of adaptive upscaling and downscaling filter selection in the VVC is demonstrated in FIG. 1. The selection modules are shown in rounded rectangles. These include a downscaling filterP24092451501WOI; G25N20990W (4824-70001) selection and an adaptive upscaling filter selection. The detailed steps in the adaptive upscaling filter selection module are explained as follows:

[0091] A preliminary list of three upscaling filter candidates is chosen. The motion compensation filter (12 taps for luma and 6 taps for chroma) from the Enhanced Compression Model (ECM) and its altered version are the two predefined candidates.

[0092] Wiener filters (8 taps for luma and 6 taps for chroma), as the third candidate, are trained online at the frame level for the luma (Y) and two chroma including blue difference chroma (Cb) and red difference chroma (Cr) planes.

[0093] An additional Wiener filter is trained for jointly optimizing the Mean Square Error (MSE) of the Cb and Cr planes altogether. Although the jointly trained Wiener filter does not minimize the MSE for Cb and Cr planes as effectively as separate filters, it saves half the bits needed to transmit Wiener coefficients for both channels.

[0094] The number of bits for Wiener coefficients after predictive coding and the signaling bits for the three filter types (1 for the default, 2 for others) are considered during rate-distortion optimization (RDO). If the joint Wiener filter is selected, no additional filter type signaling is required for each chroma channel.

[0095] The selected filter information is written in the bitstream and embedded with the RPR frame. In the reference picture list, the filter info blocks of the RPR frames are marked in the rectangles with dashed line boundary, meaning that it’s optional to use the adaptive filter when they are referred to in the motion compensation, depending on the standard altered or not.

[0096] After determining the upscaling filter, downscaling filter selection is presented as follows:

[0097] A preliminary list of candidates at the frame level is initialized to choose from. An example in WC includes the default cosine windowed sine filter with 0.9 it cutoff frequency, tw o Lanczos filters with different cutoff frequencies, and two bicubic interpolation filters with varying low-pass performances. Adaptive downscaling filters trained online are deferred since no ground truth exists for downscaled frames.

[0098] Candidates are tested on the original frame if filter signaling in the bitstream is allowed, and the filter with the lowest rescaling distortion is chosen.

[0099] An offline criterion considering frame complexity and downscaling ratio is applied to previously decoded frames if bitstream integrity must be maintained. Filter selection is based on video sequence frame features, and cutoff frequency or low-pass smoothing is adjusted according to the downscaling ratio to satisfy the Nyquist criterion.

[0100] FIG. 2 illustrates an example pipeline of RPR frame decoding in the WC Test Model. On decoder side, a module to recover the adaptive filter information is implemented in the process of parsing theP24092451501WO1; G25N20990W (4824-70001) bitstream as shown in FIG. 2. After the frame type decoded, it can be determined if there is additional information for adaptive filter to recover. The adaptive filter is used to upscale the decoded RPR frame.

[0101] To reduce the overhead of transmitting Wiener coefficients and make the Wiener filter an effective candidate in general random access applications beyond the low-delay configuration in [8], two compression techniques for Wiener coefficients are available as follows, together with the analysis of the fundamental properties of Wiener coefficients at sub-pel positions.

[0102] Coefficients at two sub-pel positions symmetric about 1 / 2 should be symmetric. For example, if cO, cl, c2, c3 are coefficients for interpolation at the 1 / 4 sub-pel position, coefficients at the 3 / 4 position should be c3, c2, cl, cO.

[0103] Coefficients at the 1 / 2 sub-pel position should be symmetric, such as cO, cl, cl. cO.

[0104] Considering these properties during Wiener filter training, only half of the sub-pel Wiener filters should be compressed and transmitted. For the luma channel, 15 sub-pel positions are standard, and for chroma, 31 sub-pel positions, meaning a maximum of 8 sets of Wiener coefficients for luma and 16 for each chroma channel should be encoded.

[0105] Option 1. an improved prediction coding scheme using Golomb codes to encode coefficient differences.

[0106] A weighted average of previously selected Wiener filter is updated and used in predictive coding.

[0107] Zero difference is handled separately. If the difference is non-zero, the sign of coefficient difference is first encoded in 1 bit. then Golomb codes with a modulo of 4 are used to encode the absolute value of coefficient difference. The quotient is encoded in unary codes, and the remainder in binary codes. A few examples are listed in the following table.P24092451501WO1; G25N20990W (4824-70001)

[0108] As another example, coefficient differences in predictive coding can be encoded in the exponential Golomb codes with an order k. To set the modulo to be 4, k can be 2, thus providing the following codes.P24092451501WO1; G25N20990W (4824-70001)

[0109] The Wiener filter length is adjustable, and a larger modulo in Golomb codes should be used when the filter length is increased and the fixed-point format coefficients are scaled up.

[0110] If the coefficient differences are so large that the Golomb codes are too long, a part of the bits in the remainder may also be discarded, thereby a lossy Wiener filter generated, to balance the scaling distortion and the bitrate.

[0111] Option 2, entropy constrained vector quantizers (ECVQ) to cluster the Wiener coefficients at each sub-pel position, with the vector representations entropy coded, for example, in Huffman codes.5. A listing of solutions and embodiments

[0112] The detailed solution below should be considered as examples to explain general concepts. These examples should not be interpreted in a narrow way. Furthermore, these examples can be combined in any manner. The methods apply to both downscaling and upscaling steps, and anywhere when frame scaling is needed.Adaptive scaling filter selection methods

[0113] These methods can be applied at various levels, including but not limited to frame, partition, tile, CTU, block or sub-block level.1. At a simple level, adaptive filters are selected from a predefined list of candidates. a. A list of filter candidates is prepared. i. In one example, the candidate list includes motion compensation filters at sub-pel positions, pre-trained RPR filters from the VVC standard, and various bicubic and Lanczos filters commonly used for interpolation. b. A criterion is applied to compare and select scaling filters from the list. i. In one example, in the adaptive upscaling filter selection module illustrated in Figure 1, rate-distortion (RD) cost, which combines scaling distortion and the corresponding signalling bits, serves as the criterion. The filter with the lowest cost is selected during RD optimization (RDO). ii. In one example, the filter providing the least distortion is selected when quality is prioritized, provided that the overhead from the signalling bits remains within a specific limit.P24092451501WO1; G25N20990W (4824-70001) iii. In one example, within the downscaling filter selection module in Figure 1, rescaling distortions, obtained after downscaling the current frame with each filter candidate and upscaling it through an optimal upscaling filter selection mechanism, are compared and determine the best downscaling filter. iv. In one example, several frames in a video sequence are analysed, and the features of the video sequence, along with an offline-trained classifier, are used to determine the downscaling filter for the current video sequence. c. The index of the selected filter is signalled. i. In one example, the frequencies of the filter candidates are sorted, and their indices are coded in increasing code lengths as their frequencies decrease. ii. In one example, the filter indices are entropy encoded, such as using Huffman codes. iii. In one example, the signal codes of the indices are written in the bitstream and transmitted to the decoder, allowing the decoder to apply the selected filter during the scaling process. iv. In one example, the signal codes of the indices are included in the supplemental information, allowing the decoder the flexibility to decide whether to use the selected filter.2. At a more complex level, an online-trained adaptive filter is generated. a. The information regarding the adaptive filter is encoded. i. In one example, predictions of the adaptive filter coefficients are generated based on previously encoded and decoded frames, and the differences between the coefficients and predictions are entropy coded. ii. In one example, the adaptive filter coefficients are collected, and vector quantizers trained offline are used to perform lossy reconstruction of the adaptive filter. b. The online-trained adaptive filter is compared with the filter candidates in the predefined list, and the filter with the best performance is selected. i. In one example, the RD cost of the adaptive filter is computed and compared with those of the predefined filter candidates. c. If the adaptive filter is selected, its index signal bits along with its associated information are processed and transmitted, as outlined in 1 (c).Compression techniques for Wiener filter coefficients1. Wiener coefficients at two sub-pel positions that are symmetric about 1 / 2 should exhibit symmetry .P24092451501WO1; G25N20990W (4824-70001) a. In one example, if cO, c 1 , c2, c3 are the interpolation coefficients at the 1 / 4 sub-pel position, the coefficients at the 3 / 4 sub-pel position should be c3, c2, cl, cO respectively.2. Coefficients at the 1 / 2 sub-pel position should be symmetric, such as cO, cl, cl, cO.3. Wiener filters for only half of the sub-pel positions need to be compressed and transmitted. a. In one example, if the scaling precision is 1 / 16 pixel, 15 sub-pel positions are used for the luma channel, and 31 sub-pel positions for each chroma channel, requiring the encoding of a maximum of 8 sets of Wiener coefficients for luma and 16 for each chroma channel. b. In one example, coefficients of the reduced set of Wiener filters are encoded as described in 2 (a).General examples1. In above examples, the video unit may refer to the video unit may refer to colour component / sub- picture / slice / tile / coding tree unit (CTU) / CTU row / groups of CTU / coding unit (CU)Zprediction unit (PU) / transform unit (TU) / coding tree block (CTB) / coding block (CB) / prediction block(PB) / transform block (TB) / a block / sub-block of a block / sub-region within a block / any other region that contains more than one sample or pixel.2. 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 / Sequence Parameter Set (SPS) / Video Parameter Set (VPS)ZDependency Parameter Set (DPS) / decoding capability information (DCI) / picture parameter set (PPS) / Adaptation Parameter Set (APS) / slice header / tile group header.3. Whether and / or how to apply the above methods may depend on the following information: a. A message signalled in the DPS / SPS / VPS / PPS / APS / picture header / slice header / tile group header / coding tree unit (CTU)ZCoding unit (CU) / CTU row / group of CTUs / TU / PU block / Video coding unit b. Position of CU / PU / TU / block / Video coding unit c. Block dimension of current block and / or its neighbouring blocks d. Block shape of current block and / or its neighbouring blocks e. coded mode of a block, e.g., intra block copy (IBC) or non-lBC inter mode or non-IBC subblock mode f. Indication of the colour format (such as 4:2:0, 4:4:4) g. Coding tree structure h. Slice / tile group type and / or picture type i. Colour component (e.g., may be only applied on chroma components or luma component) j. Temporal layer identifier (ID)P24092451501WO1; G25N20990W (4824-70001) k. Profiles / Levels / Tiers of a standard4. A syntax element disclosed above may be binarized as a flag, a fixed length code, an EG(x) code, a unary code, a truncated unary code, a truncated binary code, etc. It can be signed or unsigned.5. A syntax element disclosed above may be coded with at least one context model. Or it may be bypass coded.6. A syntax element disclosed above may be signaled in a conditional way. a. The SE is signaled only if the corresponding function is applicable. b. The SE is signaled only if the dimensions (width and / or height) of the block satisfy a condition.7. A syntax element disclosed above may be signaled at block level / sequence level / group of pictures level / picture level / slice level / tile group level, such as in coding structures of CTU / CU / TU / PU / CTB / CB / TB / PB. or sequence header / picture header / SPS / VPS / DPS / DCI / PPS / APS / slice header / tile group header.8. The proposed method(s) may be combined with another coding tool such as affine, Multi Transform Selection (MTS), Low-Frequency Non-Separable Transform (LFNST), merge mode with motion vector difference (MMVD), Matrix-based Intra Prediction (MIP), intra sub-partitions (ISP), CrossComponent Linear Model (CCLM), convolutional cross-component model (CCCM), Symmetrical motion vector difference (SMVD), Bi-directional optical flow (BDOF), decoder-side motion vector refinement (DMVR), history-based motion vector prediction (HMVP), Template Matching, intra block copy (IBC), Palette, etc.9. The proposed method(s) may be excluded with another coding tool such as affine / MTS / LFNST / MMVD / MIP / ISP / CCLM / CCCM / SMVD / BDOF / DMVR / HMVP / Template Matching / IBC / Palette / etc. a. In one example, if the proposed method(s) is used, the excluded coding tool is disabled implicitly without signaling.10. In one example, if the excluded coding tool is used, the proposed method(s) is disabled implicitly without signaling.6. References1 1 1 Ducloux X, Diascom J L, Fautier T. Exploring the benefits of dynamic resolution encoding and support in DVB standards [J], IBC, Amsterdam, NL, 2022: 15-18.[2] Ducloux X, Gendron P, Fautier T. Improving streaming quality and bitrate efficiency with dynamic resolution selection[C] / / Proceedings of the 1st Mile-High Video Conference. 2022: 13-18.[3] Lee S H, Lee S H, Cho N I. Hybrid resolution switching method for low bit rate video coding[C] / / 2007 IEEE International Conference on Image Processing. IEEE, 2007, 6: VI-73-VI-76.P24092451501WO1; G25N20990W (4824-70001)[4] Jenab M, Amer I, Ivanovic B, et al. Content-adaptive resolution control to improve video coding efficiency[C] / / 2018 IEEE International Conference on Multimedia & ExpoWorkshops (ICMEW). IEEE, 2018: 1-4.[5] "H.266: Versatile video coding". International Telecommunication Union. Archived from the original on 21 June 2021. Retrieved 21 June 2021[6] Bross B, Wang Y K. Ye Y, et al. Overview of the versatile video coding (VVC) standard and its applications [J]. IEEE Transactions on Circuits and Systems for Video Technology, 2021, 31(10): 3736- 3764.[7] Fu T, Zhang K, Li Y, et al. A smart reference picture resampling approach for WC[C] / / 2022 Data Compression Conference (DCC). IEEE, 2022: 33-42.[8] Fu T, Zhang K, Zhang L, et al. An efficient framework of reference picture resampling (RPR) for video coding[J], IEEE Transactions on Circuits and Systems for Video Technology. 2022, 32(10): 7107-7119.

[0114] FIG. 3 is a block diagram showing an example video processing system 4000 in which various techniques disclosed herein may be implemented. Various implementations may include some or all of the components of the system 4000. The system 4000 may include input 4002 for receiving video content. The video content may be received in a raw or uncompressed format, e.g., 8 or 10 bit multi-component pixel values, or may be in a compressed or encoded format. The input 4002 may represent a network interface, a peripheral bus interface, or a storage interface. Examples of network interface include wired interfaces such as Ethernet, passive optical network (PON), etc. and wireless interfaces such as wireless fidelity (Wi-Fi) or cellular interfaces.

[0115] The system 4000 may include a coding component 4004 that may implement the various coding or encoding methods described in the present disclosure. The coding component 4004 may reduce the average bitrate of video from the input 4002 to the output of the coding component 4004 to produce a coded representation of the video. The coding techniques are therefore sometimes called video compression or video transcoding techniques. The output of the coding component 4004 may be either stored, or transmitted via a communication connected, as represented by the component 4006. The stored or communicated bitstream (or coded) representation of the video received at the input 4002 may be used by a component 4008 for generating pixel values or displayable video that is sent to a display interface 4010. The process of generating user- viewable video from the bitstream representation is sometimes called video decompression. Furthermore, while certain video processing operations are referred to as "coding" operations or tools, it will be appreciated that the coding tools or operations are used at an encoder and corresponding decoding tools or operations that reverse the results of the coding will be performed by a decoder.

[0116] Examples of a peripheral bus interface or a display interface may include universal serial bus (USB) or high definition multimedia interface (HDMI) or Displayport, and so on. Examples of storageP24092451501WO1; G25N20990W (4824-70001) interfaces include serial advanced technology attachment (SATA), peripheral component interconnect (PCI), integrated drive electronics (IDE) interface, and the like. The techniques described in the present disclosure may be embodied in various electronic devices such as mobile phones, laptops, smartphones or other devices that are capable of performing digital data processing and / or video display.

[0117] FIG. 4 is a block diagram of an example video processing apparatus 4100. The apparatus 4100 may be used to implement one or more of the methods described herein. The apparatus 4100 may be embodied in a smartphone, tablet, computer, Internet of Things (loT) receiver, and so on. The apparatus 4100 may include one or more processors 4102, one or more memories 4104 and video processing circuitry 4106. The proccssor(s) 4102 may be configured to implement one or more methods described in the present disclosure. The memory (memories) 4104 may be used for storing data and code used for implementing the methods and techniques described herein. The video processing circuitry 4106 may be used to implement, in hardware circuitry, some techniques described in the present disclosure. In some embodiments, the video processing circuitry 4106 may be at least partly included in the processor 4102, e.g., a graphics co-processor.

[0118] FIG. 5 is a flowchart for an example method 4200 of video processing. The method 4200 determines to select to select one or more adaptive scaling filters from a predefined list of candidates for a level or to generate an online-trained adaptive filter at step 4202. A conversion is performed between a visual media data and a bitstream based on the one or more adaptive scaling filters selected or online-trained adaptive filter generated at step 4204. The conversion may include encoding at an encoder, decoding at a decoder, or combinations thereof.

[0119] It should be noted that the method 4200 can be implemented in an apparatus for processing video data comprising a processor and a non-transitory memory with instructions thereon, such as video encoder 4400, video decoder 4500, and / or encoder 4600. In such a case, the instructions upon execution by the processor, cause the processor to perform the method 4200. Further, the method 4200 can be performed by a non-transitory computer readable medium comprising a computer program product for use by a video coding device. The computer program product comprises computer executable instructions stored on the non- transitory computer readable medium such that when executed by a processor cause the video coding device to perfonn the method 4200.

[0120] FIG. 6 is a block diagram that illustrates an example video coding system 4300 that may utilize the techniques of this disclosure. The video coding system 4300 may include a source device 4310 and a destination device 4320. Source device 4310 generates encoded video data which may be referred to as a video encoding device. Destination device 4320 may decode the encoded video data generated by source device 4310 which may be referred to as a video decoding device.

[0121] Source device 4310 may include a video source 4312, a video encoder 4314, and an input / output (I / O) interface 4316. Video source 4312 may include a source such as a video capture device, an interface toP24092451501WO1; G25N20990W (4824-70001) receive video data from a video content provider, and / or a computer graphics system for generating video data, or a combination of such sources. The video data may comprise one or more pictures. Video encoder 4314 encodes the video data from video source 4312 to 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. I / O interface 4316 may include a modulator / demodulator (modem) and / or a transmitter. The encoded video data may be transmitted directly to destination device 4320 via I / O interface 4316 through network 4330. The encoded video data may also be stored onto a storage medium / server 4340 for access by destination device 4320.

[0122] Destination device 4320 may include an I / O interface 4326, a video decoder 4324, and a display device 4322. I / O interface 4326 may include a receiver and / or a modem. I / O interface 4326 may acquire encoded video data from the source device 4310 or the storage medium / server 4340. Video decoder 4324 may decode the encoded video data. Display device 4322 may display the decoded video data to a user. Display device 4322 may be integrated with the destination device 4320, or may be external to destination device 4320, which can be configured to interface with an external display device.

[0123] Video encoder 4314 and video decoder 4324 may operate according to a video compression standard, such as the High Efficiency Video Coding (HEVC) standard. Versatile Video Coding (WC) standard and other current and / or further standards.

[0124] FIG. 7 is a block diagram illustrating an example of video encoder 4400, which may be video encoder 4314 in the system 4300 illustrated in FIG. 6. Video encoder 4400 may be configured to perform any or all of the techniques of this disclosure. The video encoder 4400 includes a plurality of functional components. The techniques described in this disclosure may be shared among the various components of video encoder 4400. In some examples, a processor may be configured to perform any or all of the techniques described in this disclosure.

[0125] The functional components of video encoder 4400 may include a partition unit 4401, a prediction unit 4402 which may include a mode select unit 4403, a motion estimation unit 4404, a motion compensation unit 4405, an intra prediction unit 4406, a residual generation unit 4407, a transform processing unit 4408, a quantization unit 4409, an inverse quantization unit 4410, an inverse transform unit 4411, a reconstruction unit 4412, a buffer 4413, and an entropy encoding unit 4414.

[0126] In other examples, video encoder 4400 may include more, fewer, or different functional components. In an example, prediction unit 4402 may include an intra block copy (IBC) unit. The IBC unit may perform prediction in an IBC mode in which at least one reference picture is a picture where the current video block is located.P24092451501WO1; G25N20990W (4824-70001)

[0127] Furthermore, some components, such as motion estimation unit 4404 and motion compensation unit 4405 may be highly integrated, but are represented in the example of video encoder 4400 separately for purposes of explanation.

[0128] Partition unit 4401 may partition a picture into one or more video blocks. Video encoder 4400 and video decoder 4500 may support various video block sizes.

[0129] Mode select unit 4403 may select one of the coding modes, intra or inter, e.g., based on error results, and provide the resulting intra or inter coded block to a residual generation unit 4407 to generate residual block data and to a reconstruction unit 4412 to reconstruct the encoded block for use as a reference picture. In some examples, mode select unit 4403 may select a combination of intra and inter prediction (CIIP) mode in which the prediction is based on an inter prediction signal and an intra prediction signal. Mode select unit 4403 may 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 prediction.

[0130] To perform inter prediction on a current video block, motion estimation unit 4404 may generate motion information for the current video block by comparing one or more reference frames from buffer 4413 to the current video block. Motion compensation unit 4405 may determine a predicted video block for the current video block based on the motion information and decoded samples of pictures from buffer 4413 other than the picture associated with the current video block.

[0131] Motion estimation unit 4404 and motion compensation unit 4405 may perform different operations for a current video block, for example, depending on whether tire current video block is in an I slice, a P slice, or a B slice.

[0132] In some examples, motion estimation unit 4404 may perform uni-directional prediction for the current video block, and motion estimation unit 4404 may search reference pictures of list 0 or list 1 for a reference video block for the current video block. Motion estimation unit 4404 may then generate a reference index that indicates the reference picture in list 0 or list 1 that contains the reference video block and a motion vector that indicates a spatial displacement between the current video block and the reference video block. Motion estimation unit 4404 may output the reference index, a prediction direction indicator, and the motion vector as the motion information of the current video block. Motion compensation unit 4405 may generate the predicted video block of the current block based on the reference video block indicated by the motion information of the current video block.

[0133] In other examples, motion estimation unit 4404 may perfonn bi-directional prediction for the current video block, motion estimation unit 4404 may search the reference pictures in list 0 for a reference video block for the current video block and may also search the reference pictures in list 1 for another reference video block for the current video block. Motion estimation unit 4404 may then generate reference indexes that indicate the reference pictures in list 0 and list 1 containing the reference video blocks and motion vectors thatP24092451501WO1; G25N20990W (4824-70001) indicate spatial displacements between the reference video blocks and the current video block. Motion estimation unit 4404 may output the reference indexes and the motion vectors of the current video block as the motion information of the current video block. Motion compensation unit 4405 may generate the predicted video block of the current video block based on the reference video blocks indicated by the motion information of the current video block.

[0134] In some examples, motion estimation unit 4404 may output a fall set of motion information for decoding processing of a decoder. In some examples, motion estimation unit 4404 may not output a fall set of motion information for the current video. Rather, motion estimation unit 4404 may signal the motion information of the current video block with reference to the motion information of another video block. For example, motion estimation unit 4404 may determine that the motion information of the current video block is sufficiently similar to the motion information of a neighboring video block.

[0135] In one example, motion estimation unit 4404 may indicate, in a syntax structure associated with the current video block, a value that indicates to the video decoder 4500 that the current video block has the same motion information as another video block.

[0136] In another example, motion estimation unit 4404 may identify, in a syntax structure associated with the current video block, another video block and a motion vector difference (MVD). The motion vector difference indicates a difference between the motion vector of the current video block and the motion vector of the indicated video block. The video decoder 4500 may use the motion vector of the indicated video block and the motion vector difference to determine the motion vector of the current video block.

[0137] As discussed above, video encoder 4400 may predictively signal the motion vector. Two examples of predictive signaling techniques that may be implemented by video encoder 4400 include advanced motion vector prediction (AMVP) and merge mode signaling.

[0138] Intra prediction unit 4406 may perform intra prediction on the current video block. When intra prediction unit 4406 performs intra prediction on the current video block, intra prediction unit 4406 may 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.

[0139] Residual generation unit 4407 may generate residual data for the current video block by subtracting the predicted video block(s) of the current video block from the current video block. The residual data of the current video block may include residual video blocks that correspond to different sample components of the samples in the current video block.

[0140] 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 residual generation unit 4407 may not perform the subtracting operation.P2409245150IWO1; G25N20990W (4824-70001)

[0141] Transform processing unit 4408 may generate one or more transform coefficient video blocks for the current video block by applying one or more transforms to a residual video block associated with the current video block.

[0142] After transform processing unit 4408 generates a transform coefficient video block associated with the current video block, quantization unit 4409 may 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.

[0143] Inverse quantization unit 4410 and inverse transform unit 4411 may 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. Reconstruction unit 4412 may add the reconstructed residual video block to corresponding samples from one or more predicted video blocks generated by the prediction unit 4402 to produce a reconstructed video block associated with the current block for storage in the buffer 4413.

[0144] After reconstruction unit 4412 reconstructs the video block, the loop filtering operation may be performed to reduce video blocking artifacts in the video block.

[0145] Entropy encoding unit 4414 may receive data from other functional components of the video encoder 4400. When entropy encoding unit 4414 receives the data, entropy encoding unit 4414 may perform one or more entropy encoding operations to generate entropy encoded data and output a bitstream that includes the entropy encoded data.

[0146] FIG. 8 is a block diagram illustrating an example of video decoder 4500 which may be video decoder 4324 in the system 4300 illustrated in FIG. 6. The video decoder 4500 may be configured to perform any or all of the techniques of this disclosure. In the example shown, the video decoder 4500 includes a plurality of functional components. The techniques described in this disclosure may be shared among the various components of the video decoder 4500. In some examples, a processor may be configured to perform any or all of the techniques described in this disclosure.

[0147] In the example shown, video decoder 4500 includes an entropy decoding unit 4501, a motion compensation unit 4502, an intra prediction unit 4503, an inverse quantization unit 4504, an inverse transformation unit 4505, a reconstruction unit 4506, and a buffer 4507. Video decoder 4500 may, in some examples, perform a decoding pass generally reciprocal to the encoding pass described with respect to video encoder 4400.

[0148] Entropy decoding unit 4501 may retrieve an encoded bitstream. The encoded bitstream may include entropy coded video data (e.g., encoded blocks of video data). Entropy decoding unit 4501 may decode the entropy coded video data, and from the entropy decoded video data, motion compensation unit 4502 may determine motion information including motion vectors, motion vector precision, reference pictureP24092451501WO1; G25N20990W (4824-70001) list indexes, and other motion information. Motion compensation unit 4502 may, for example, determine such information by performing the AM VP and merge mode.

[0149] Motion compensation unit 4502 may produce motion compensated blocks, possibly performing interpolation based on interpolation filters. Identifiers for interpolation filters to be used with sub-pixel precision may be included in the syntax elements.

[0150] Motion compensation unit 4502 may use interpolation filters as used by video encoder 4400 during encoding of the video block to calculate interpolated values for sub-integer pixels of a reference block. Motion compensation unit 4502 may determine the interpolation filters used by video encoder 4400 according to received syntax information and use the interpolation filters to produce predictive blocks.

[0151] Motion compensation unit 4502 may use some 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 coded block, and other information to decode the encoded video sequence.

[0152] Intra prediction unit 4503 may use intra prediction modes for example received in the bitstream to form a prediction block from spatially adjacent blocks. Inverse quantization unit 4504 inverse quantizes, i.e., de-quantizes, the quantized video block coefficients provided in the bitstream and decoded by entropy decoding unit 4501. Inverse transform unit 4505 applies an inverse transform.

[0153] Reconstruction unit 4506 may sum the residual blocks with the corresponding prediction blocks generated by motion compensation unit 4 02 or intra prediction unit 4 03 to form decoded blocks. 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 buffer 4507, which provides reference blocks for subsequent motion compensation / intra prediction and also produces decoded video for presentation on a display device.

[0154] FIG. 9 is a schematic diagram of an example encoder 4600. The encoder 4600 is suitable for implementing the techniques of WC. The encoder 4600 includes three in-loop filters, namely a deblocking filter (DF) 4602. a sample adaptive offset (SAO) 4604, and an adaptive loop filter (ALF) 4606. Unlike the DF 4602, which uses predefined filters, the SAO 4604 and the ALF 4606 utilize the original samples of the current picture to reduce the mean square errors between the original samples and the reconstructed samples by adding an offset and by applying a finite impulse response (FIR) filter, respectively, with coded side information signaling the offsets and filter coefficients. The ALF 4606 is located at the last processing stage of each picture and can be regarded as a tool trying to catch and fix artifacts created by the previous stages.

[0155] The encoder 4600 further includes an intra prediction component 4608 and a motion estimation / compensation (ME / MC) component 4610 configured to receive input video. The intra prediction component 4608 is configured to perform intra prediction, while the ME / MC component 4610 is configuredP24092451501WO1; G25N20990W (4824-70001) to utilize reference pictures obtained from a reference picture buffer 4612 to perform inter prediction. Residual blocks from inter prediction or intra prediction are fed into a transform (T) component 4614 and a quantization (Q) component 4616 to generate quantized residual transform coefficients, which are fed into an entropy coding component 4618. The entropy coding component 4618 entropy codes the prediction results and the quantized transform coefficients and transmits the same toward a video decoder (not shown). Quantization components output from the quantization component 4616 may be fed into an inverse quantization (IQ) components 4620, an inverse transform component 4622, and a reconstruction (REC) component 4624. The REC component 4624 is able to output images to the DF 4602, the SAG 4604, and the ALF 4606 for filtering prior to those images being stored in the reference picture buffer 4612.

[0156] A listing of solutions preferred by some examples is provided next.

[0157] The following solutions show examples of techniques discussed herein.

[0158] 1. A method for processing media data comprising: determining to select one or more adaptive scaling filters; and performing a conversion between a visual media data and a bitstream based on the adaptive scaling filters.

[0159] 2. The method of solution 1, wherein the adaptive scaling filters are selected from a predefined list of candidates.

[0160] 3. The method of any of solutions 1-2, wherein a candidate list of filter candidates is prepared, and wherein the candidate list includes motion compensation filters at sub-pel positions, pre-trained reference picture resample (RPR) filters, bicubic filters, and Lanczos filters.

[0161] 4. The method of any of solutions 1-3, wherein a criterion is applied to compare and select scaling filters from the candidate list.

[0162] 5. The method of any of solutions 1 -4, wherein in an adaptive upscaling filter selection module, rate-distortion (RD) cost, which combines scaling distortion and corresponding signalling bits, serves as the criterion, and wherein the filter with the lowest cost is selected during RD optimization (RDO).

[0163] 6. The method of any of solutions 1-5, wherein a filter providing the least distortion is selected when quality is prioritized, provided that overhead from the signalling bits remains within a specific limit.

[0164] 7. The method of any of solutions 1-6, wherein within a downscaling filter selection module, rescaling distortions are compared and determine a best downscaling filter, and wherein rescaling distortions are obtained after downscaling a current frame with each filter candidate and upscaling the current frame through an optimal upscaling filter selection.

[0165] 8. The method of any of solutions 1 -7, wherein a plurality of frames in a current video sequence are analyzed, and wherein features of the video sequence and an offline-trained classifier are used to determine a downscaling filter for a current video sequence.P24092451501WO1; G25N20990W (4824-70001)

[0166] 9. The method of any of solutions 1 -8, wherein an index of a selected filter is signalled.

[0167] 10. The method of any of solutions 1-9, wherein frequencies of a filter candidates are sorted, and filter candidate indices are coded in increasing code lengths as the filter candidate frequencies decrease.

[0168] 11. The method of any of solutions 1-10, wherein filter indices are entropy encoded usingHuffman codes.

[0169] 12. The method of any of solutions 1-11, wherein signal codes of indices are coded in the bitstream and transmitted to allow application of a selected filter during a scaling process.

[0170] 13. The method of any of solutions 1-12, wherein signal codes of indices are included in supplemental enhancement information to allow a determination of whether to use a selected filter.

[0171] 14. The method of any of solutions 1-13, wherein the adaptive scaling filters are selected by generating an online-trained adaptive filter.

[0172] 15. The method of any of solutions 1-14. wherein information regarding the adaptive scaling filters is encoded in the bitstream.

[0173] 16. The method of any of solutions 1-15, wherein predictions of adaptive filter coefficients are generated based on previously encoded and decoded frames, and differences between coefficients and predictions are entropy coded, or wherein the adaptive filter coefficients are collected, and vector quantizers trained offline are used to perform lossy reconstruction of the adaptive filter.

[0174] 17. The method of any of solutions 1-16, wherein the online-trained adaptive filter is compared with filter candidates in a predefined list, and a filter with a best performance is selected, or wherein a rate distortion (RD) cost of the adaptive filter is computed and compared with RD costs of the filter candidates.

[0175] 18. The method of any of solutions 1-17, wherein when an adaptive scaling filter is selected, signal bits of an index of the adaptive scaling filter and associated information are processed and transmitted.

[0176] 19. The method of any of solutions 1-18, wherein Wiener coefficients at two sub-pel positions that are symmetric about 1 / 2 exhibit symmetry.

[0177] 20. The method of any of solutions 1-19, wherein when cO, cl, c2, and c3 are the interpolation coefficients at the 1 / 4 sub-pel position, the coefficients at the 3 / 4 sub-pel position are c3, c2, cl. and cO, respectively.

[0178] 21. The method of any of solutions 1-20, wherein coefficients at a 1 / 2 sub-pel position are symmetric, or wherein coefficients at a 1 / 2 sub-pel position are cO, cl, cl, and cO.

[0179] 22. The method of any of solutions 1-21, wherein Wiener filters for only half of the sub-pel positions are be compressed and transmitted.

[0180] 23. The method of any of solutions 1-22, wherein when a scaling precision is 1 / 16 pixel, 15 sub- pel positions are used for a luma channel, and 31 sub-pel positions are used for each chroma channel, andP24092451501WO1; G25N20990W (4824-70001) wherein a maximum of 8 sets of Wiener coefficients for luma and 16 for each chroma channel are included in the bitstream.

[0181] 24. The method of any of solutions 1-23, wherein coefficients of a reduced set of Wiener filters are included in the bitstream.

[0182] 25. The method of any of solutions 1-24. wherein the video unit includes a sequence, picture, sub-picture, slice, tile, coding tree unit (CTU), CTU row, groups of CTU, coding unit (CU), prediction unit (PU), transform unit (TU), coding tree block (CTB), coding block (CB), prediction block (PB), transform block (TB), or any other region that contains more than one luma or chroma sample or pixel.

[0183] 26. The method of any of solutions 1-25, wherein application of the methods is signalled in a bitstream, or wherein they are signalled at sequence level, group of pictures level, picture level, slice level, or tile group level, in sequence header, picture header, sequence parameter set (SPS), video parameter set (VPS), decoding parameter set (DPS), decoding capability information (DCI), picture parameter set (PPS), Adaptation Parameter Set (APS), slice header, or tile group header.

[0184] 27. The method of any of solutions 1-26. wherein whether to or how to apply the method is dependent on a message signalled in a DPS. SPS, VPS, PPS, APS, picture header, slice header, tile group header, CTU, CU, CTU row, group of CTUs, TU, PU block, video coding unit, position of CU, PU, TU, block, video coding unit, block dimension of current block or block dimension of neighbouring blocks, block shape of current block or block shape of neighbouring blocks, coded mode of a block including IBC, non- IBC inter mode, or non-IBC subblock mode, indication of the colour format, coding tree structure, slice type, tile group type, picture type, colour component, temporal layer identifier (ID), profiles, levels, orders.

[0185] 28. The method of any of solutions 1-27, wherein a syntax element is binarized as a flag, a fixed length code, an EG(x) code, a unary code, a truncated unary code, or a truncated binary code, and wherein the syntax element is signed or unsigned.

[0186] 29. The method of any of solutions 1-28, wherein a syntax element is coded with at least one context model or is bypass coded.

[0187] 30. The method of any of solutions 1-29, wherein a syntax element is signaled in a conditional way, or wherein the syntax element is signaled only w hen the corresponding function is applicable, or wherein the syntax element is signaled only when the dimensions including width or height of the block satisfy a condition.

[0188] 31. The method of any of solutions 1-30, wherein a syntax element is signaled at block level, sequence level, group of pictures level, picture level, slice level, or tile group level, in coding structures CTU, CU, TU, PU, CTB, CB, TB, PB, sequence header, picture header, SPS, VPS, DPS, DCI, PPS, APS, slice header, or tile group header.P24092451501WOI; G25N20990W (4824-70001)

[0189] 32. The method of any of solutions 1-31, wherein the method is combined with another coding tool including affine, Multi Transform Selection (MTS), Low-Frequency Non-Separable Transform (LFNST), merge mode with motion vector difference (MMVD), Matrix-based Intra Prediction (MIP), intra sub-partitions (ISP). Cross-Component Linear Model (CCLM), convolutional cross-component model (CCCM), Symmetrical motion vector difference (SMVD), Bi-directional optical flow (BDOF), decoder-side motion vector refinement (DMVR), history-based motion vector prediction (HMVP), Template Matching, intra block copy (IBC), or Palette.

[0190] 33. The method of any of solutions 1-32, wherein the method is excluded from another coding tool including affine, MTS, LFNST, MMVD, MIP, ISP, CCLM. CCCM, SMVD, BDOF, DMVR, HMVP, Template Matching, IBC, or Palette, or wherein when the method is used, the excluded coding tool is disabled implicitly without signaling, or wherein when the excluded coding tool is used, the method is disabled implicitly without signaling.

[0191] 34. 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 perfonn the method of any of solutions 1-33.

[0192] 35. A non-transitory computer readable medium comprising a computer program product for use by a video coding device, the computer program product comprising computer executable instructions stored on the non-transitory computer readable medium such that when executed by a processor cause the video coding device to perform the method of any of solutions 1-33.

[0193] 36. A non-transitory computer-readable recording medium storing a bitstream of a video which is generated by a method performed by a video processing apparatus, wherein the method comprises: determining to select one or more adaptive scaling filters; and generating a bitstream based on the determining.

[0194] 37. A method for storing bitstream of a video comprising: determining to select one or more adaptive scaling filters; generating a bitstream based on tire determining; and storing the bitstream in a non- transitory computer-readable recording medium.

[0195] 38. A method, apparatus, or system described in the present disclosure.

[0196] In the solutions described herein, an encoder may conform to the format rule by producing a coded representation according to the format rule. In the solutions described herein, a decoder may use the format rule to parse syntax elements in the coded representation with the knowledge of presence and absence of syntax elements according to the format rule to produce decoded video.

[0197] In the present disclosure, the term “video processing” may refer to video encoding, video decoding, video compression or video decompression. For example, video compression algorithms may be applied during conversion from pixel representation of a video to a corresponding bitstream representation or vice versa. The bitstream representation of a current video block may, for example, correspond to bits that areP24092451501WO1; G25N20990W (4824-70001) either co-located or spread in different places within the bitstream, as is defined by the syntax. For example, a macroblock may be encoded in terms of transformed and coded error residual values and also using bits in headers and other fields in the bitstream. Furthermore, during conversion, a decoder may parse a bitstream with the knowledge that some fields may be present, or absent, based on the determination, as is described in the above solutions. Similarly, an encoder may determine that certain syntax fields are or are not to be included and generate the coded representation accordingly by including or excluding the syntax fields from the coded representation.

[0198] The disclosed and other solutions, examples, embodiments, modules and the functional operations described in this disclosure can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this disclosure and their structural equivalents, or in combinations of one or more of them. The disclosed and other embodiments can be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a computer readable medium for execution by, or to control the operation of, data processing apparatus. The computer readable medium can be a machine-readable storage device, a machine- readable storage substrate, a memory device, a composition of matter effecting a machine-readable propagated signal, or a combination of one or more them. The term “data processing apparatus” encompasses all apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, or multiple processors or computers. The apparatus can include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them. A propagated signal is an artificially generated signal, e.g., a machinegenerated electrical, optical, or electromagnetic signal, that is generated to encode information for transmission to suitable receiver apparatus.

[0199] A computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, sub programs, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network.

[0200] The processes and logic flows described in this disclosure can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating onP24092451501WO1; G25N20990W (4824-70001) input data and generating output. The processes and logic flows can also be performed by, and apparatus can also be implemented as, special purpose logic circuitry, e.g., a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC).

[0201] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read only memory or a random-access memory or both. The essential elements of a computer are a processor for performing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto optical disks, or optical disks. However, a computer need not have such devices. Computer readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., erasable programmable read-only memory (EPROM), electrically erasable programmable readonly memory (EEPROM), and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto optical disks; and compact disc read-only memory (CD ROM) and Digital versatile disc-read only memory (DVD-ROM) disks. The processor and the memory can be supplemented by, or incorporated in. special purpose logic circuitry.

[0202] While the present disclosure contains many specifics, these should not be construed as limitations on the scope of any subject matter or of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular techniques. Certain features that arc described in the present disclosure in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

[0203] Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Moreover, the separation of various system components in the embodiments described in the present disclosure should not be understood as requiring such separation in all embodiments.

[0204] Only a few implementations and examples are described and other implementations, enhancements and variations can be made based on what is described and illustrated in the present disclosure.P24092451501WO1; G25N20990W (4824-70001)

[0205] A first component is directly coupled to a second component when there are no intervening components, except for a line, a trace, or another medium between the first component and the second component. The first component is indirectly coupled to the second component when there arc intervening components other than a line, a trace, or another medium between the first component and the second component. The term “coupled” and its variants include both directly coupled and indirectly coupled. The use of the term “about” means a range including ±10% of the subsequent number unless otherwise stated.

[0206] While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and methods might be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted, or not implemented.

[0207] In addition, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items shown or discussed as coupled may be directly connected or may be indirectly coupled or communicating through some interface, device, or intermediate component whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the spirit and scope disclosed herein.

Claims

P24092451501WO1; G25N20990W (4824-70001)CLAIMSWhat is claimed is:

1. A method for processing media data, comprising: determining to select one or more adaptive scaling filters from a predefined list of candidates for a level or to generate an online-trained adaptive filter; and performing a conversion between a visual media data and a bitstream based on the one or more adaptive scaling filters selected or online-trained adaptive filter generated.

2. The method of claim 1. wherein the level comprises a frame, a partition, a tile, a coding tree unit (CTU), a block, or a sub-block.

3. The method of any of claims 1-2, further comprising preparing the pre-defined list of candidates.

4. The method of any of claims 1-3, wherein the pre-defined list of candidates comprises motion compensation filters at sub-pel positions, pre-trained reference picture resample (RPR) filters, bicubic filters, and Lanczos filters.

5. The method of any of claims 1-4, further comprising applying a criterion to compare and select the one or more scaling filters from the predefined list of candidates.

6. The method of claim 5, wherein the criterion comprises a rate-distortion cost.

7. The method of claim 6, wherein the rate-distortion cost combines scaling distortion and corresponding signaling bits.

8. The method of any of claims 6-7, wherein an adaptive upscaling filter is determined by an adaptive upscaling filter module.

9. The method of any of claims 6-8, wherein a filter providing a lowest cost is selected during ratedistortion optimization (RDO).P24092451501WO1; G25N20990W (4824-70001)10. The method of any of claims 6-8, wherein a filter providing a lowest distortion is selected when quality is prioritized and when overhead from signaling bits remains within a specific limit.

11. The method of any of claims 1-4, further comprising comparing rescaling distortions to determine a downscaling filter.

12. The method of claim 11, wherein the rescaling distortions are obtained after a current frame has been downscaled with each filter candidate and upscaling the current frame with an upscaling filter.

13. The method of claim 12, wherein the upscaling filter is determined by an upscaling filter selection mechanism.

14. The method of any of claims 1-13, further comprising analyzing several frames in a video sequence.

15. The method of claim 14, wherein features of the video sequence and an offline-trained classifier are used to determine a downscaling filter for the video sequence.

16. The method of any of claims 1-15. wherein the bitstream includes an index of the one or more scaling filters selected.

17. The method of claim 16, further comprising sorting frequencies of the one or more scaling filters selected.

18. The method of claim 17. wherein filter indices of the frequencies are coded in increasing code lengths as frequencies decrease.

19. The method of claim 18, further comprising entropy encoding the filter indices.

20. The method of claim 18, further comprising entropy encoding the filter indices using Huffman codes.

21. The method of claim 16, wherein signal codes of filter indices are included in the bitstream.P24092451501WO1; G25N20990W (4824-70001)22. The method of claim 21, wherein the signal codes instruct a decoder to apply the one or more adaptive scaling filters selected.

23. The method of claim 16, wherein signal codes of filter indices are included in supplemental information.

24. The method of claim 23, wherein the signal codes permit a decoder to determine whether or not to apply the one or more adaptive scaling filters selected.

25. The method of claim 1, wherein the online-trained adaptive filter is encoded in the bitstream.

26. The method of any of claims 1-2, further comprising generating predictions of the online-trained adaptive filter based on at least one of previously encoded frames and previously decoded frames.

27. The method of claim 26, wherein differences between the predictions of the online-trained adaptive filter and coefficients of the online-trained adaptive filter are entropy coded.

28. The method of claim 25, further comprising collecting coefficients of the online-trained adaptive filter.

29. The method of claim 28, further comprising performing lossy reconstruction of the online-trained adaptive filter using vector quantizers trained offline.

30. The method of claim 25, further comprising comparing the online-trained adaptive filter with filter candidates in the predefined list of candidates.

31. The method of claim 30, further comprising selecting one of the filter candidates with a best performance.

32. The method of claim 30, further comprising computing the rate distortion (RD) cost of the online- trained adaptive filter and comparing the RD cost of the online-trained adaptive filter with the filter candidates in the predefined list of candidates.P24092451501WO1; G25N20990W (4824-70001)33. The method of claim 25, further comprising processing index signal bits along with corresponding information when the online-trained adaptive filter is selected.

34. The method of claim 33, further comprising transmitting the processing index signal bits and the corresponding information.

35. The method of any of claims 1-34, wherein coefficients for the one or more adaptive scaling filters or the online-trained adaptive filter comprise Wiener coefficients.

36. The method of claim 35, wherein the Wiener coefficients at two sub-pel positions that are symmetric about 1 / 2 exhibit symmetry.

37. The method of any of claims 35-36, wherein the coefficients at the 3 / 4 sub-pel position are c3, c2, cl, and cO when the coefficients at the 1 / 4 sub-pel position are cO, cl, c2, and c3, respectively.

38. The method of claim 35, wherein the coefficients at the 1 / 2 sub-pel position are symmetric.

39. The method of claim 38, wherein the coefficients comprise cO, cl, cl. cO.

40. The method of claim 35, wherein Wiener filters for only half of the sub-pel positions are compressed and transmitted.

41. The method of claim 40, wherein 15 sub-pel positions are used for a luma channel and 31 sub-pel positions are used for each chroma channel when the scaling precision is 1 / 16 pixel.

42. The method of claim 41, wherein a maximum of 8 sets of the Wiener coefficients for the luma channel and 16 sets of the Wiener coefficients for each chroma channel are included in the bitstream.

43. The method of any of claims 41-42. wherein coefficients of a reduced set of the Weiner filters are included in the bitstream.

44. The method of any of claims 1-43, wherein the visual media data includes a video unit, and wherein the video unit comprises a sequence, picture, sub-picturc, slice, tile, coding tree unit (CTU), CTU row, groups of CTU, coding unit (CU), prediction unit (PU), transform unit (TU), coding tree block (CTB), coding blockP24092451501WO1; G25N20990W (4824-70001)(CB), prediction block (PB), transform block (TB), or any other region that contains more than one luma or chroma sample or pixel.

45. The method of any of claims 1-44, wherein whether to and / or how to apply one or more of the methods is indicated in the bitstream at sequence level, group of pictures level, picture level, slice level, or tile group level, or in a sequence header, picture header, sequence parameter set (SPS), video parameter set (VPS), decoding parameter set (DPS), decoding capability information (DO), picture parameter set (PPS), Adaptation Parameter Set (APS), slice header, or tile group header.

46. The method of any of claims 1-45, wherein whether to or how to apply one or more of the methods is dependent on: a message included in a DPS, SPS, VPS, PPS. APS. picture header, slice header, tile group header, CTU, CU, CTU row, group of CTUs, TU, PU block, or video coding unit: a position of CU, PU, TU, block, or video coding unit; a block dimension of current block or a block dimension of neighbouring blocks; a block shape of current block or a block shape of neighbouring blocks: a coded mode of a block including intra block copy (IBC) mode, non-IBC inter mode, or non-IBC subblock mode; an indication of a colour format; a coding tree structure; a slice type, tile group type, or picture type; a colour component only applied on chroma components or luma components; a temporal layer identifier (ID); or a profile, level, or tier.

47. The method of any of claims 1-46, wherein a syntax element in the bitstream is binarized as a flag, a fixed length code, an EG(x) code, a unary code, a truncated unary’ code, or a truncated binary code, and wherein the syntax element is signed or unsigned.

48. The method of any of claims 1-47, wherein a syntax element in the bitstream is coded with at least one context model or is bypass coded.

49. The method of any of claims 1-48, wherein a syntax element is signaled in a conditional w ay.P24092451501WO1; G25N20990W (4824-70001)50. The method of claim 49, wherein the syntax element is in the bitstream only when the corresponding function is applicable.

51. The method of claim 49, wherein the syntax element is in the bitstream only when dimensions including width or height of a block satisfy a condition.

52. The method of any of claims 1-51, wherein a syntax element is included in the bitstream at a block level, sequence level, group of pictures level, picture level, slice level, or tile group level, or in one or more coding structures comprising a coding tree unit (CTU), coding unit (CU), transform unit (TU), prediction unit (PU), coding tree block (CTB), coding block (CB), transform block (TB), prediction block (PB), sequence header, picture header, sequence parameter set (SPS), video parameter set (VPS), dependency parameter set (DPS), decoding capability information (DCI). picture parameter set (PPS), adaptation parameter set (APS), slice header, or tile group header.

53. The method of any of claims 1-52, wherein the method is combined with another coding tool including affine, Multi Transform Selection (MTS), Low-Frequency Non-Separable Transform (LFNST), merge mode with motion vector difference (MMVD). Matrix-based Intra Prediction (MIP), intra subpartitions (ISP), Cross-Component Linear Model (CCLM), convolutional cross-component model (CCCM), Symmetrical motion vector difference (SMVD), Bi-directional optical flow (BDOF), decoder-side motion vector refinement (DMVR), histor -based motion vector prediction (HMVP), Template Matching, intra block copy (IBC), or Palette.

54. The method of any of claims 1-32, wherein the method is excluded from being used with another coding tool including affine. MTS, LFNST. MMVD, MIP, ISP. CCLM, CCCM, SMVD. BDOF. DMVR, HMVP, Template Matching, IBC, or Palette.

55. The method of claim 54, wherein the excluded coding tool is disabled implicitly without signaling when the method is used.

56. The method of claim 54, wherein the method is disabled implicitly without signaling when the excluded coding tool is used.

57. The method of any of claims 1-56, wherein the conversion includes encoding the visual media data into the bitstream.P24092451501WO1; G25N20990W (4824-70001)58. The method of any of claims 1-56, wherein the conversion includes decoding the visual media data from the bitstream.

59. 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 the method of any of claims 1-58.

60. A non-transitory computer readable medium comprising a computer program product for use by a video coding device, the computer program product comprising computer executable instructions stored on the non-transitory computer readable medium such that when executed by a processor cause the video coding device to perform the method of any of claims 1-58.

61. A non-transitory computer-readable recording medium storing a bitstream of a video which is generated by a method performed by a video processing apparatus, wherein the method comprises: determining to select one or more adaptive scaling filters from a predefined list of candidates for a level or to generate an online-trained adaptive filter; and generating a bitstream based on the determination.

62. A method for storing bitstream of a video comprising: determining to select one or more adaptive scaling filters from a predefined list of candidates for a level or to generate an online-trained adaptive filter; generating a bitstream based on the determination; and storing the bitstream in a non-transitory computer-readable recording medium.

63. A method, apparatus, or system described in the present disclosure.

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