WO2024061330A1

WO2024061330A1 - Method, apparatus, and medium for video processing

Info

Publication number: WO2024061330A1
Application number: PCT/CN2023/120483
Authority: WO
Inventors: Junru LI; Ye-Kui Wang; Kai Zhang; Li Zhang; Yue Li; Chaoyi Lin
Original assignee: Douyin Vision Co., Ltd.; Bytedance Inc.
Priority date: 2022-09-21
Filing date: 2023-09-21
Publication date: 2024-03-28

Abstract

Embodiments of the present disclosure provide a solution for video processing. A method for video processing is proposed. The method comprises: performing a conversion between a current video unit of a video and a bitstream of the video, wherein the bitstream comprises at least one set of syntax elements for activating at least one neural-network post-filter (NNPF) for the current video unit, and the current video unit is a portion of a picture of the video.

Description

METHOD, APPARATUS, AND MEDIUM FOR VIDEO PROCESSING

FIELDS

Embodiments of the present disclosure relates generally to video processing techniques, and more particularly, to extension of neural-network post-filter activation and neural-network post-filter characteristics.

BACKGROUND

In nowadays, digital video capabilities are being applied in various aspects of peoples’ lives. Multiple types of video compression technologies, such as MPEG-2, MPEG-4, ITU-TH. 263, ITU-TH. 264/MPEG-4 Part 10 Advanced Video Coding (AVC) , ITU-TH. 265 high efficiency video coding (HEVC) standard, versatile video coding (VVC) standard, have been proposed for video encoding/decoding. However, coding quality of video coding techniques is generally expected to be further improved.

SUMMARY

Embodiments of the present disclosure provide a solution for video processing.

In a first aspect, a method for video processing is proposed. The method comprises: performing a conversion between a current video unit of a video and a bitstream of the video, wherein the bitstream comprises at least one set of syntax elements for activating at least one neural-network post-filter (NNPF) for the current video unit, and the current video unit is a portion of a picture of the video.

According to the method in accordance with the first aspect of the present disclosure, the activation of one or more NNPFs for a portion of a picture of the video may be controlled with the at least one set of syntax elements. In other words, the activation of one or more NNPFs may be controlled at a level lower than the picture level, such as a slice level, a tile level or the like. Compared with the conventional solution, where the activation of one or more NNPFs is controlled at the picture level, the proposed method can advantageously enable the application of NNPF in a refined manner, and thus the coding quality can be improved.

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

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

In a fourth aspect, another non-transitory computer-readable recording medium is proposed. The non-transitory computer-readable recording medium stores a bitstream of a video which is generated by a method performed by an apparatus for video processing. The method comprises: performing a conversion between a current video unit of the video and the bitstream, wherein the bitstream comprises at least one set of syntax elements for activating at least one neural-network post-filter (NNPF) for the current video unit, and the current video unit is a portion of a picture of the video.

In a fifth aspect, a method for storing a bitstream of a video is proposed. The method comprises: performing a conversion between a current video unit of the video and the bitstream, wherein the bitstream comprises at least one set of syntax elements for activating at least one neural-network post-filter (NNPF) for the current video unit, and the current video unit is a portion of a picture of the video; and storing the bitstream in a non-transitory computer-readable recording medium.

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

Through the following detailed description with reference to the accompanying drawings, the above and other objectives, features, and advantages of example embodiments of the present disclosure will become more apparent. In the example embodiments of the present disclosure, the same reference numerals usually refer to the same components.

Fig. 1 illustrates a block diagram that illustrates an example video coding system, in accordance with some embodiments of the present disclosure;

Fig. 2 illustrates a block diagram that illustrates a first example video encoder, in accordance with some embodiments of the present disclosure;

Fig. 3 illustrates a block diagram that illustrates an example video decoder, in accordance with some embodiments of the present disclosure;

Fig. 4 illustrates an example of raster-scan slice partitioning of a picture;

Fig. 5 illustrates an example of rectangular slice partitioning of a picture;

Fig. 6 illustrates an example of a picture partitioned into tiles and rectangular slices;

Fig. 7 illustrates an example of subpicture partitioning of a picture;

Fig. 8A illustrates an example of CTBs crossing picture borders;

Fig. 8B illustrates a further example 802 of CTBs crossing picture borders;

Fig. 8C illustrates a still further example 804 of CTBs crossing picture borders;

Fig. 9 illustrates an illustration of luma data channels;

Fig. 10 illustrates a flowchart of a method for video processing in accordance with embodiments of the present disclosure; and

Fig. 11 illustrates a block diagram of a computing device in which various embodiments of the present disclosure can be implemented.

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

DETAILED DESCRIPTION

Principle of the present disclosure will now be described with reference to some embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones described below.

In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

References in the present disclosure to “one embodiment, ” “an embodiment, ” “an example embodiment, ” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an example embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

It shall be understood that although the terms “first” and “second” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the listed terms.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a” , “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” , “comprising” , “has” , “having” , “includes” and/or “including” , when used herein, specify the presence of stated features, elements, and/or components etc., but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof.

Example Environment

Fig. 1 is a block diagram that illustrates an example video coding system 100 that may utilize the techniques of this disclosure. As shown, the video coding system 100 may include a source device 110 and a destination device 120. The source device 110 can be also referred to as a video encoding device, and the destination device 120 can be also referred to as a video decoding device. In operation, the source device 110 can be configured to generate encoded video data and the destination device 120 can be configured to decode the encoded video data generated by the source device 110. The source device 110 may include a video source 112, a video encoder 114, and an input/output (I/O) interface 116.

The video source 112 may include a source such as a video capture device. Examples of the video capture device include, but are not limited to, an interface to receive video data from a video content provider, a computer graphics system for generating video data, and/or a combination thereof.

The video data may comprise one or more pictures. The video encoder 114 encodes the video data from the video source 112 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. The I/O interface 116 may include a modulator/demodulator and/or a transmitter. The encoded video data may be transmitted directly to destination device 120 via the I/O interface 116 through the network 130A. The encoded video data may also be stored onto a storage medium/server 130B for access by destination device 120.

The destination device 120 may include an I/O interface 126, a video decoder 124, and a display device 122. The I/O interface 126 may include a receiver and/or a modem. The I/O interface 126 may acquire encoded video data from the source device 110 or the storage medium/server 130B. The video decoder 124 may decode the encoded video data. The display device 122 may display the decoded video data to a user. The display device 122 may be integrated with the destination device 120, or may be external to the destination device 120 which is configured to interface with an external display device.

The video encoder 114 and the video decoder 124 may operate according to a video compression standard, such as the High Efficiency Video Coding (HEVC) standard, Versatile Video Coding (VVC) standard and other current and/or further standards.

Fig. 2 is a block diagram illustrating an example of a video encoder 200, which may be an example of the video encoder 114 in the system 100 illustrated in Fig. 1, in accordance with some embodiments of the present disclosure.

The video encoder 200 may be configured to implement any or all of the techniques of this disclosure. In the example of Fig. 2, the video encoder 200 includes a plurality of functional components. The techniques described in this disclosure may be shared among the various components of the video encoder 200. In some examples, a processor may be configured to perform any or all of the techniques described in this disclosure.

In some embodiments, the video encoder 200 may include a partition unit 201, a prediction unit 202 which may include a mode select unit 203, a motion estimation unit 204, a motion compensation unit 205 and an intra-prediction unit 206, a residual generation unit 207, a transform unit 208, a quantization unit 209, an inverse quantization unit 210, an inverse transform unit 211, a reconstruction unit 212, a buffer 213, and an entropy encoding unit 214.

In other examples, the video encoder 200 may include more, fewer, or different functional components. In an example, the prediction unit 202 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.

Furthermore, although some components, such as the motion estimation unit 204 and the motion compensation unit 205, may be integrated, but are represented in the example of Fig. 2 separately for purposes of explanation.

The partition unit 201 may partition a picture into one or more video blocks. The video encoder 200 and the video decoder 300 may support various video block sizes.

The mode select unit 203 may select one of the coding modes, intra or inter, e.g., based on error results, and provide the resulting intra-coded or inter-coded block to a residual generation unit 207 to generate residual block data and to a reconstruction unit 212 to reconstruct the encoded block for use as a reference picture. In some examples, the mode select unit 203 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. The mode select unit 203 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.

To perform inter prediction on a current video block, the motion estimation unit 204 may generate motion information for the current video block by comparing one or more reference frames from buffer 213 to the current video block. The motion compensation unit 205 may determine a predicted video block for the current video block based on the motion information and decoded samples of pictures from the buffer 213 other than the picture associated with the current video block.

The motion estimation unit 204 and the motion compensation unit 205 may perform different operations for a current video block, for example, depending on whether the current video block is in an I-slice, a P-slice, or a B-slice. As used herein, an “I-slice” may refer to a portion of a picture composed of macroblocks, all of which are based upon macroblocks within the same picture. Further, as used herein, in some aspects, “P-slices” and “B-slices” may refer to portions of a picture composed of macroblocks that are not dependent on macroblocks in the same picture.

In some examples, the motion estimation unit 204 may perform uni-directional prediction for the current video block, and the motion estimation unit 204 may search reference pictures of list 0 or list 1 for a reference video block for the current video block. The motion estimation unit 204 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. The motion estimation unit 204 may output the reference index, a prediction direction indicator, and the motion vector as the motion information of the current video block. The motion compensation unit 205 may generate the predicted video block of the current video block based on the reference video block indicated by the motion information of the current video block.

Alternatively, in other examples, the motion estimation unit 204 may perform bi-directional prediction for the current video block. The motion estimation unit 204 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. The motion estimation unit 204 may then generate reference indexes that indicate the reference pictures in list 0 and list 1 containing the reference video blocks and motion vectors that indicate spatial displacements between the reference video blocks and the current video block. The motion estimation unit 204 may output the reference indexes and the motion vectors of the current video block as the motion information of the current video block. The motion compensation unit 205 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.

In some examples, the motion estimation unit 204 may output a full set of motion information for decoding processing of a decoder. Alternatively, in some embodiments, the motion estimation unit 204 may signal the motion information of the current video block with reference to the motion information of another video block. For example, the motion estimation unit 204 may determine that the motion information of the current video block is sufficiently similar to the motion information of a neighboring video block.

In one example, the motion estimation unit 204 may indicate, in a syntax structure associated with the current video block, a value that indicates to the video decoder 300 that the current video block has the same motion information as the another video block.

In another example, the motion estimation unit 204 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 300 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.

As discussed above, video encoder 200 may predictively signal the motion vector. Two examples of predictive signaling techniques that may be implemented by video encoder 200 include advanced motion vector prediction (AMVP) and merge mode signaling.

The intra prediction unit 206 may perform intra prediction on the current video block. When the intra prediction unit 206 performs intra prediction on the current video block, the intra prediction unit 206 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.

The residual generation unit 207 may generate residual data for the current video block by subtracting (e.g., indicated by the minus sign) 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.

In other examples, there may be no residual data for the current video block for the current video block, for example in a skip mode, and the residual generation unit 207 may not perform the subtracting operation.

The transform processing unit 208 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.

After the transform processing unit 208 generates a transform coefficient video block associated with the current video block, the quantization unit 209 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.

The inverse quantization unit 210 and the inverse transform unit 211 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. The reconstruction unit 212 may add the reconstructed residual video block to corresponding samples from one or more predicted video blocks generated by the prediction unit 202 to produce a reconstructed video block associated with the current video block for storage in the buffer 213.

After the reconstruction unit 212 reconstructs the video block, loop filtering operation may be performed to reduce video blocking artifacts in the video block.

The entropy encoding unit 214 may receive data from other functional components of the video encoder 200. When the entropy encoding unit 214 receives the data, the entropy encoding unit 214 may perform one or more entropy encoding operations to generate entropy encoded data and output a bitstream that includes the entropy encoded data.

Fig. 3 is a block diagram illustrating an example of a video decoder 300, which may be an example of the video decoder 124 in the system 100 illustrated in Fig. 1, in accordance with some embodiments of the present disclosure.

The video decoder 300 may be configured to perform any or all of the techniques of this disclosure. In the example of Fig. 3, the video decoder 300 includes a plurality of functional components. The techniques described in this disclosure may be shared among the various components of the video decoder 300. In some examples, a processor may be configured to perform any or all of the techniques described in this disclosure.

In the example of Fig. 3, the video decoder 300 includes an entropy decoding unit 301, a motion compensation unit 302, an intra prediction unit 303, an inverse quantization unit 304, an inverse transformation unit 305, and a reconstruction unit 306 and a buffer 307. The video decoder 300 may, in some examples, perform a decoding pass generally reciprocal to the encoding pass described with respect to video encoder 200.

The entropy decoding unit 301 may retrieve an encoded bitstream. The encoded bitstream may include entropy coded video data (e.g., encoded blocks of video data) . The entropy decoding unit 301 may decode the entropy coded video data, and from the entropy decoded video data, the motion compensation unit 302 may determine motion information including motion vectors, motion vector precision, reference picture list indexes, and other motion information. The motion compensation unit 302 may, for example, determine such information by performing the AMVP and merge mode. AMVP is used, including derivation of several most probable candidates based on data from adjacent PBs and the reference picture. Motion information typically includes the horizontal and vertical motion vector displacement values, one or two reference picture indices, and, in the case of prediction regions in B slices, an identification of which reference picture list is associated with each index. As used herein, in some aspects, a “merge mode” may refer to deriving the motion information from spatially or temporally neighboring blocks.

The motion compensation unit 302 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.

The motion compensation unit 302 may use the interpolation filters as used by the video encoder 200 during encoding of the video block to calculate interpolated values for sub-integer pixels of a reference block. The motion compensation unit 302 may determine the interpolation filters used by the video encoder 200 according to the received syntax information and use the interpolation filters to produce predictive blocks.

The motion compensation unit 302 may use at least part of the syntax information to determine sizes of blocks used to encode frame (s) and/or slice (s) of the encoded video sequence, partition information that describes how each macroblock of a picture of the encoded video sequence is partitioned, modes indicating how each partition is encoded, one or more reference frames (and reference frame lists) for each inter-encoded block, and other information to decode the encoded video sequence. As used herein, in some aspects, a “slice” may refer to a data structure that can be decoded independently from other slices of the same picture, in terms of entropy coding, signal prediction, and residual signal reconstruction. A slice can either be an entire picture or a region of a picture.

The intra prediction unit 303 may use intra prediction modes for example received in the bitstream to form a prediction block from spatially adjacent blocks. The inverse quantization unit 304 inverse quantizes, i.e., de-quantizes, the quantized video block coefficients provided in the bitstream and decoded by entropy decoding unit 301. The inverse transform unit 305 applies an inverse transform.

The reconstruction unit 306 may obtain the decoded blocks, e.g., by summing the residual blocks with the corresponding prediction blocks generated by the motion compensation unit 302 or intra-prediction unit 303. If desired, a deblocking filter may also be applied to filter the decoded blocks in order to remove blockiness artifacts. The decoded video blocks are then stored in the buffer 307, which provides reference blocks for subsequent motion compensation/intra prediction and also produces decoded video for presentation on a display device.

Some exemplary embodiments of the present disclosure will be described in detailed hereinafter. It should be understood that section headings are used in the present document to facilitate ease of understanding and do not limit the embodiments disclosed in a section to only that section. Furthermore, while certain embodiments are described with reference to Versatile Video Coding or other specific video codecs, the disclosed techniques are applicable to other video coding technologies also. Furthermore, while some embodiments describe video coding steps in detail, it will be understood that corresponding steps decoding that undo the coding will be implemented by a decoder. Furthermore, the term video processing encompasses video coding or compression, video decoding or decompression and video transcoding in which video pixels are represented from one compressed format into another compressed format or at a different compressed bitrate.

1. Brief Summary

This disclosure is related to image/video coding technologies. Specifically, it is related to usage and controlling for neural network post processing filters signaled in a video bitstream. Herein usage and controlling can be applied in a video unit (e.g., picture/slice/CTU) . The ideas may be applied individually or in various combinations, for video bitstreams coded by any codec, e.g., the versatile video coding (VVC) standard and/or the versatile SEI messages for coded video bitstreams (VSEI) standard.

2. Abbreviations
APS   Adaptation Parameter Set
AU    Access Unit
CLVS  Coded Layer Video Sequence
CLVSS Coded Layer Video Sequence Start
CRC   Cyclic Redundancy Check
CVS   Coded Video Sequence
FIR   Finite Impulse Response
IRAP  Intra Random Access Point
NAL   Network Abstraction Layer
PPS   Picture Parameter Set
PU    Picture Unit
RASL  Random Access Skipped Leading
SEI   Supplemental Enhancement Information
STSA  Step-wise Temporal Sublayer Access
VCL   Video Coding Layer
VSEI  versatile supplemental enhancement information (Rec. ITU-T H. 274 |
ISO/IEC 23002-7)
VUI   Video Usability Information
VVC   versatile video coding (Rec. ITU-T H. 266 | ISO/IEC 23090-3)

3. Introduction

3.1. Video coding standards

Video coding standards have evolved primarily through the development of the well-known ITU-T and ISO/IEC standards. The ITU-T produced H. 261 and H. 263, ISO/IEC produced MPEG-1 and MPEG-4 Visual, and the two organizations jointly produced the H. 262/MPEG-2 Video and H. 264/MPEG-4 Advanced Video Coding (AVC) and H. 265/HEVC standards. Since H. 262, the video coding standards are based on the hybrid video coding structure wherein temporal prediction plus transform coding are utilized. To explore the future video coding technologies beyond HEVC, the Joint Video Exploration Team (JVET) was founded by VCEG and MPEG jointly in 2015. Since then, many new methods have been adopted by JVET and put into the reference software named Joint Exploration Model (JEM) . The JVET was later renamed to be the Joint Video Experts Team (JVET) when the Versatile Video Coding (VVC) project officially started. VVC is the new coding standard, targeting at 50%bitrate reduction as compared to HEVC, that has been finalized by the JVET at its 19th meeting ended at July 1, 2020.

The Versatile Video Coding (VVC) standard (ITU-T H. 266 | ISO/IEC 23090-3) and the associated Versatile Supplemental Enhancement Information for coded video bitstreams (VSEI) standard (ITU-T H. 274 | ISO/IEC 23002-7) have been designed for use in a maximally broad range of applications, including both the traditional uses such as television broadcast, video conferencing, or playback from storage media, and also newer and more advanced use cases such as adaptive bit rate streaming, video region extraction, composition and merging of content from multiple coded video bitstreams, multiview video, scalable layered coding, and viewport-adaptive 360° immersive media.

The Essential Video Coding (EVC) standard (ISO/IEC 23094-1) is another video coding standard that has recently been developed by MPEG.

3.2. Definitions of video units

A picture is divided into one or more tile rows and one or more tile columns. A tile is a sequence of CTUs that covers a rectangular region of a picture. The CTUs in a tile are scanned in raster scan order within that tile.

A slice consists of an integer number of complete tiles or an integer number of consecutive complete CTU rows within a tile of a picture. Consequently, each vertical slice boundary is always also a vertical tile boundary. It is possible that a horizontal boundary of a slice is not a tile boundary but consists of horizontal CTU boundaries within a tile; this occurs when a tile is split into multiple rectangular slices, each of which consists of an integer number of consecutive complete CTU rows within the tile.

Two modes of slices are supported, namely the raster-scan slice mode and the rectangular slice mode. In the raster-scan slice mode, a slice contains a sequence of complete tiles in a tile raster scan of a picture. In the rectangular slice mode, a slice contains either a number of complete tiles that collectively form a rectangular region of the picture or a number of consecutive complete CTU rows of one tile that collectively form a rectangular region of the picture. Tiles within a rectangular slice are scanned in tile raster scan order within the rectangular region corresponding to that slice.

A subpicture contains one or more slices that collectively cover a rectangular region of a picture. Consequently, each subpicture boundary is also always a slice boundary, and each vertical subpicture boundary is always also a vertical tile boundary.

One or both of the following conditions shall be fulfilled for each subpicture and tile:

– All CTUs in a subpicture belong to the same tile.

– All CTUs in a tile belong to the same subpicture.

Fig. 4 shows an example of raster-scan slice partitioning of a picture, where the picture is divided into 12 tiles and 3 raster-scan slices. More specifically, a picture with 18 by 12 luma CTUs is partitioned into 12 tiles and 3 raster-scan slices. Fig. 5 shows an example of rectangular slice partitioning of a picture, where the picture is divided into 24 tiles (6 tile columns and 4 tile rows) and 9 rectangular slices. More specifically, a picture with 18 by 12 luma CTUs is partitioned into 24 tiles and 9 rectangular slices. Fig. 6 shows an example of a picture partitioned into tiles and rectangular slices, where the picture is divided into 4 tiles (2 tile columns and 2 tile rows) and 4 rectangular slices. Fig. 7 shows an example of subpicture partitioning of a picture, where a picture is partitioned into 18 tiles, 12 tiles on the left-hand side each covering one slice of 4 by 4 CTUs and 6 tiles on the right-hand side each covering 2 vertically-stacked slices of 2 by 2 CTUs, altogether resulting in 24 slices and 24 subpictures of varying dimensions (each slice is a subpicture) .

3.2.1. CTU/CTB sizes

In VVC, the CTU size, signaled in SPS by the syntax element log2_ctu_size_minus2, could be as small as 4x4.

3.2.2. CTUs in a picture

Suppose the CTB/LCU size indicated by M x N (typically M is equal to N, as defined in HEVC/VVC) , and for a CTB located at picture (or tile or slice or other kinds of types, picture border is taken as an example) border, K x L samples are within picture border wherein either K<M or L<N. For those CTBs as depicted in Figs. 8A-8C, the CTB size is still equal to MxN, however, the bottom boundary/right boundary of the CTB is outside the picture. Fig. 8A is a diagram 800 illustrating an example of CTBs crossing picture borders, where K=M, L<N, and CTBs cross the bottom picture border. Fig. 8B is a diagram 802 illustrating a further example of CTBs crossing picture borders, where K<M, L=N, and CTBs cross the right picture border. Fig. 8C is a diagram 804 illustrating a still further example of CTBs crossing picture borders, where K<M, L<N and CTBs cross the right bottom picture border.

3.3. SEI messages in general and in VVC and VSEI

SEI messages assist in processes related to decoding, display or other purposes. However, SEI messages are not required for constructing the luma or chroma samples by the decoding process. Conforming decoders are not required to process this information for output order conformance. Some SEI messages are required for checking bitstream conformance and for output timing decoder conformance. Other SEI messages are not required for check bitstream conformance. Annex D of VVC specifies syntax and semantics for SEI message payloads for some SEI messages, and specifies the use of the SEI messages and VUI parameters for which the syntax and semantics are specified in ITU-T H. 274 | ISO/IEC 23002-7.

3.4. Signalling of neural-network post-filters

An existing design includes the specification of two SEI messages for signalling of neural-network post-filters, as follows.

4. Problems

There are some problems in the current design of neural-network post-filter activation (NNPFA) and neural-network post-filter characteristics (NNPFC) SEI message.

1) The NNPFA and/or NNPFC SEI message persists only for the current picture. However, the neural-network post-processing filter (NNPF) may be effective only for part region of the current picture, such as slice, coding tree unit, coding unit, coding block, region of in-terest. And NNPF may be also effective for whole sequence such that it is efficient to only signal one NNPFA and/or NNPFC message instead of signal NNPFA and/or NNPFC mes-sage for every picture. Therefore, it is necessary to supplement certain region information into NNPFA and/or NNPFC.

2) There may be several NNPFA and/or NNPFC SEI messages present for the same picture. And only one post-processing filter specified by nnpfa_id is activated in one SEI message. However, various content in video unit (such as picture, slice, coding unit, etc.. ) may require different post-processing filters. Multiple set of filters may be useful for different content such that multiple groups of syntax elements for multiple sets of filters should be added into one NNPFA and/or NNPFC SEI message and how to use/switch the post-processing filters for video units need to be supplemented in NNPFA and/or NNPFC SEI message.

3) The neural-network post-processing filter could improve the performance of visual quality. Generally speaking, NNPF with higher complexity may produce better performance im-provement. In current design, SEI message only provides the complexity characteristic. But the performance characteristic is ignored.

5. Detailed Solutions

To solve the above problems, methods as summarized below are disclosed. The solutions should be considered as examples to explain the general concepts and should not be interpreted in a narrow way. Furthermore, these solutions can be applied individually or combined in any manner.

1) It is proposed that the activation and/or enabling and/or presence and/or usage of neural-network post-filter (NNPF) for video units may be controlled by one or multiple groups of syntax elements in a video message unit.

a. In one example, the video message unit may be a SEI message, such as NNPFA SEI message.

b. In one example, the group of syntax elements may be expressed as SE_activa-tion.

i. In one example, SE_activation may comprise multiple syntax elements.

1. In one example, nnpfa_id may be involved in SE_activation.

2. In one example, the number of NNPF may be involved in SE_ac-tivation.

3. In one example, purpose of range information of color compo-nents may be involved in SE_activation.

4. In one example, the range of color components may be involved in SE_activation.

c. A video unit may be whole or part or sub-region of a video/sequence/image in the following bullets.

i. In one example, video unit may be a sequence.

ii. In one example, video unit may be a picture.

iii. In one example, video unit may be a slice.

iv. In one example, video unit may be a tile/brick.

v. In one example, video unit may be a subpicture.

vi. In one example, video unit may be one or multiple CTUs/CTBs.

vii. In one example, video unit may be a CTU/CTB row.

viii. In one example, video unit may be one or multiple CUs/CBs.

ix. In one example, video unit may be one or multiple VPDU (Virtual Pipe-line Data Unit) .

x. In one example, video unit may be a sub-region within a pic-ture/slice/tile/brick.

d. A video unit may be one or multiple patches of picture in the following bullets.

i. In one example, patch is a rectangular array of samples from a compo-nent of a picture.

1. In one example, component may be a luma or chroma component.

2. In one example, component may be a Y or U (Cb) or V (Cr) com-ponent.

3. In one example, component may be a R or G or B component.

ii. In one example, patch may be defined in the video message.

1. In one example, patch size may be acquired from NNPFC SEI message.

a. In one example, the patch width may be nnpfc_patch_width_minus1 + 1.

b. In one example, the patch height may be multiple of (nnpfc_patch_width_minus1 + 1) .

c. In one example, the patch width may be nnpfc_patch_height_minus1 + 1.

d. In one example, the patch height may be multiple of (nnpfc_patch_height_minus1 + 1) .

e. A video unit may be one or multiple regions of interest (ROI) in the following bullets.

i. In one example, one ROI may include one or multiple initial point.

1. In one example, initial point may include horizontal coordinate (x₀) .

2. In one example, initial point may include vertical coordinate (y₀) .

ii. In one example, one ROI may include one or multiple ending point.

1. In one example, ending point may include horizontal coordinate (x_n) .

2. In one example, ending point may include vertical coordinate (y_n) .

iii. In one example, one ROI may include one or multiple size information.

1. In one example, one ROI may include horizontal samples (width) of region.

2. In one example, one ROI may include vertical samples (height) of region.

iv. In one example, one ROI may be specified or decided according to the output of applying image/video segmentation algorithms on the decoded output picture.

1. In one example, all foreground regions are considered as ROI.

2. In one example, all background regions are considered as ROI.

3. In one example, regions corresponding to certain types of content (e.g. car, people, cat, sky, etc. ) are considered as ROI.

v. In one example, one ROI may be specified or decided according to the output of applying image/video object classification/detection algo-rithms on the decoded output picture.

1. In one example, regions corresponding to certain/all classes of detected objects are considered as ROI.

2. In one example, regions not containing any detected objects are considered as ROI.

f. In one example, whether one or multiple groups of syntax elements should be applied to a video unit (such as a picture or a slice) may depend on the relative relationship when signaling the video unit and the video message unit.

i. In one example, one or multiple groups of syntax elements should be applied to a video unit signaled after the video message unit.

ii. In one example, one or multiple groups of syntax elements should be applied to a video unit signaled before the video message unit.

2) The group of syntax elements (expressed as SE_activation) indicating the activation and/or enabling and/or presence and/or usage may depend on color components and/or color formats.

a. In one example, syntax elements (expressed as SE_color_purpose) indicating the purpose of range information of color components may be added into NNPFA SEI message.

i. In one example, one (1^st) purpose may be that only one group of SE_ac-tivation need to be involved in NNPFA SEI message and the activation and/or enabling and/or presence and/or usage controlled by SE_activa-tion are commonly used for available color components specified in NNPFC SEI message.

1. In one example, the NNPFC SEI message may define the availa-ble color components for a post-processing filter identified by syntax element nnpfc_id or it is limited that the filter can be only used for specific color components which are determined by the design of the post filer.

2. In one example, the value of one syntax element of SE_color_purpose equal to 0 specifies 1^st purpose.

ii. In one example, one (2^nd) purpose may be that only one group of SE_ac-tivation need to be involved in NNPFA SEI message and the activation and/or enabling and/or presence and/or usage controlled by SE_activa-tion are commonly used for all color components in specified color range (SE_color_range in the following discussion) .

1. In one example, the value of one syntax element of SE_color_purpose equal to 1 specifies 2^nd purpose.

iii. In one example, one (3^rd) purpose may be that multiple groups of SE_ac-tivation need to be involved in NNPFA SEI message and need to be used for different color components in specified color range (SE_color_range in the following discussion) .

1. In one example, the value of one syntax element of SE_color_purpose equal to 2 specifies 3^rd purpose.

iv. In one example, the syntax elements SE_color_purpose may be not sig-naled.

1. In one example, one purpose (in above discussion or not) may be set as default purpose.

b. In one example, syntax elements (expressed as SE_color_range) indicating the range of color components may be added into NNPFA SEI message. SE_acti-vation may be used for all color components in specified color range indicated by SE_color_range.

i. In one example, the usage of SE_color_range may be depended on the SE_color_purpose.

1. In one example, when the value of one syntax element of SE_color_purpose equals to 1 or 2 (be equivalent to the 2^nd pur-pose or 3^rd purpose in the above discussion) the SE_color_range may be signaled.

2. In one example, when the value of one syntax element of SE_color_purpose equals to 0 (be equivalent to the 1^st purpose in the above discussion) the SE_color_range may be not sig-naled.

ii. In one example, SE_activation may be used for color components in specified color range indicated by SE_color_range.

1. In one example, one group of SE_activation need to be involved in NNPFA SEI message and is commonly used for all available color components.

2. In one example, multiple groups of SE_activation need to be in-volved in NNPFA SEI message and are used for different avail-able color components.

a. In one example, the number of groups of SE_activation may equal to the number of available color components.

iii. In one example, color range may include Y and/or U (Cb) and/or V (Cr) component.

iv. In one example, color range may include R and/or G and/or B component.

v. In one example, the max number of color components in color range may be 3, 2, 1.

c. In one example, the syntax elements (expressed as SE_activation) may be uni-fied for more than one color components.

i. In one example, the syntax elements may indicate the activation and/or enabling and/or presence and/or usage of all color component.

1. In one example, color components include Y and/or Cb and/or Cr components.

2. In one example, color components include R and/or G and/or B components.

ii. In one example, the syntax elements may indicate the activation and/or enabling and/or presence and/or usage of chroma components.

1. In one example, color components include Cb and Cr compo-nents.

d. In one example, the syntax elements (expressed as SE_activation) may be sep-arate for color components.

i. In one example, the syntax elements may be different for all color com-ponents.

1. In one example, first group of syntax elements may be used for first color component.

a. In one example, first color component may be Y and/or Cb and/or Cr components.

b. In one example, first color component may be R and/or G and/or B components.

2. In one example, second group of syntax elements may be used for second color component.

a. In one example, second color component may be Cb and/or Y and/or Cr components.

b. In one example, second color component may be G and/or R and/or B components.

3. In one example, third group of syntax elements may be used for third color component.

a. In one example, third color component may be Cr and/or Y and/or Cb components.

b. In one example, third color component may be B and/or G and/or R components.

ii. In one example, the syntax elements (expressed as SE_activation) may be different for luma and chroma color components.

1. In one example, first group of syntax elements may be used for luma component.

2. In one example, second group of syntax elements may be used for chroma component.

a. In one example, second group of syntax elements may be same for Cb and Cr components.

3) How to/whether to signal the group of syntax elements (expressed as SE_activation) indi-cating the activation and/or enabling and/or presence and/or usage may depend on the num-ber of NNPF.

a. In one example, one or more syntax elements indicating the number of NNPF may be added into NNPFA SEI message.

i. In one example, the syntax element may be expressed as nnpfa_num_minus1.

1. In one example, the number of NNPF may be equal to nnpfa_num_minus1 + 1.

2. In one example, the value of nnpfa_num_minus1 shall be in the range of 0 to 2^k -1, inclusive.

a. In one example, k may be integer, such as 0, 1, 2, 3, 4, 5, 6, 7, …, 32.

ii. In one example, the number of NNPF may be ue (v) -coded.

b. In one example, the number of NNPF may be smaller than the max value of nnpfc_id plus one.

c. In one example, the number of NNPF may be not signaled into NNPFA SEI message.

i. In one example, the number of NNPF may be set as default value.

ii. In one example, the number of NNPF may be 1.

4) One or more syntax elements indicating the identification of NNPF may be added into NNPFA SEI message.

a. In one example, identification of NNPF may be nnpfa_id.

b. In one example, identification of NNPF may be involved in SE_activation.

c. In one example, more than one of identification of NNPF may be added into NNPFA SEI message.

d. In one example, the number of identifications of NNPF may depend on the color component.

e. In one example, the number of identifications of NNPF may depend on the num-ber of NNPF.

5) One or more syntax elements (expressed as SE_region_type) indicating the region type of NNPF may be added into NNPFA and/or NNPFC SEI message.

a. In one example, region type of NNPF may be involved in SE_activation.

i. In one example, region type of NNPF may be nnpfa_region_type.

b. In one example, a region may be one type of video unit.

c. In one example, one or more syntax elements indicating the region scope (SE_region_scope) of NNPF may be added into NNPFA SEI message for cor-responding region type.

i. In one example, region scope of NNPF may be involved in SE_activa-tion.

1. In one example, region scope of NNPF may be involved when region type is ROI.

ii. In one example, region scope may depend on the region type.

iii. In one example, region scope may be or be NOT signaled when the re-gion type is identical to setting value.

1. In one example, region type is a picture.

d. In one example, a region may be whole or part or sub-region of a video/se-quence/image.

i. In one example, a region may be a sequence.

ii. In one example, a region may be a picture.

iii. In one example, a region may be a slice.

iv. In one example, a region may be a tile/brick.

v. In one example, a region may be a subpicture.

vi. In one example, a region may be one or multiple CTUs/CTBs.

1. In one example, one or more syntax elements indicating the iden-tification of CTUs/CTBs of NNPF may be added into NNPFA SEI message when the region type is CTUs/CTBs.

a. In one example, identification of CTUs/CTBs may be in-dicated by coordinate.

b. In one example, identification of CTUs/CTBs may be in-dicated by index one by one (in sequence) .

vii. In one example, a region may be a CTU/CTB row.

1. In one example, one or more syntax elements indicating the iden-tification of CTU/CTB row of NNPF may be added into NNPFA SEI message when the region type is CTU/CTB row.

a. In one example, identification of CTU/CTB row may be indicated by coordinate of CTU/CTB row.

b. In one example, identification of CTU/CTB row may be indicated by index of CTU/CTB row one by one (in se-quence) .

viii. In one example, a region may be one or multiple CUs/CBs.

1. In one example, one or more syntax elements indicating the iden-tification of CUs/CBs of NNPF may be added into NNPFA SEI message when the region type is CTUs/CTBs.

a. In one example, identification of CUs/CBs may be indi-cated by coordinate.

b. In one example, identification of CUs/CBs may be indi-cated by index one by one (in sequence) .

ix. In one example, a region may be one or multiple VPDU (Virtual Pipeline Data Unit) .

1. In one example, one or more syntax elements indicating the iden-tification of VPDU of NNPF may be added into NNPFA SEI message when the region type is CTUs/CTBs.

a. In one example, identification of VPDU may be indicated by coordinate.

b. In one example, identification of VPDU may be indicated by index one by one (in sequence) .

x. In one example, a region may be a sub-region within a pic-ture/slice/tile/brick.

e. In one example, a region may be one or multiple patches of picture.

i. In one example, one or more syntax elements indicating the size of patch of NNPF may be added into NNPFA SEI message when the region type is patch.

ii. In one example, one or more syntax elements indicating the horizontal and/or vertical and/or total number of patches of NNPF may be added into NNPFA SEI message when the region type is patch.

f. In one example, a region may be one or multiple regions of interest (ROI) .

i. In one example, one or more syntax elements indicating the initial point of ROI of NNPF may be added into NNPFA SEI message when the re-gion type is ROI.

ii. In one example, one or more syntax elements indicating the ending point of ROI of NNPF may be added into NNPFA SEI message when the re-gion type is ROI.

iii. In one example, one or more syntax elements indicating the horizontal samples (width) of ROI of NNPF may be added into NNPFA SEI mes-sage when the region type is ROI.

iv. In one example, one or more syntax elements indicating the vertical sam-ples (height) of ROI of NNPF may be added into NNPFA SEI message when the region type is ROI.

g. In one example, region type of NNPF may be NOT signaled.

i. In one example, region type may be set as a default type.

1. In one example, region type may be picture level.

ii. In one example, region type may have a lowest level.

1. In one example, lowest level of region type may be patch level.

iii. In one example, usage and/or switch and/or activation of NNPF may be indicated by a certain order.

1. In one example, sequence level may be applied before picture level.

6) One or more syntax elements indicating usage and/or switch and/or activation of NNPF may be added into NNPFA SEI message.

a. The syntax elements may depend on the region type.

i. In one example, only syntax elements at the region level of specified region type may be added into NNPFA SEI message.

1. In one example, NNPFA SEI message may comprise syntax ele-ment indicating NNPF at picture level when region type is picture.

2. In one example, NNPFA SEI message may comprise syntax ele-ment indicating NNPF at slice level when region type is slice.

3. In one example, NNPFA SEI message may comprise syntax ele-ment indicating NNPF at CTU level when region type is CTU.

b. One or more syntax elements indicating usage of NNPF at the region (video unit) level may be added into NNPFA SEI message.

i. In one example, syntax elements for different region level may be sig-naled following certain order.

1. In one example, syntax element of higher region level may be signaled before lower region level.

ii. In one example, one syntax element may indicate whether the NNPF is used in the current region level.

1. In one example, syntax element equal to 0 may indicates that the NNPF is not used in current region.

2. In one example, syntax element equal to 1 may indicates that the NNPF is used in current region.

3. In one example, syntax element greater than 0 may indicates that the NNPF is used in current region.

iii. In one example, one syntax element may indicate how to select the NNPF in the current region level or which NNPF is used in the current region level.

1. In one example, syntax element greater than 0 may indicates that the NNPF with index (syntax element -1) is used in current re-gion.

2. In one example, syntax element smaller than maxNnpfNum may indicates that the NNPF with index (syntax element) is used in current region.

iv. In one example, one syntax element may indicate whether the NNPF is adaptively used in the next (lower) region level.

1. In one example, syntax element equal to 0 may indicates that the NNPF is adaptively selected in next region level.

2. In one example, syntax element equal to maxNnpfNum may in-dicates that the NNPF is adaptively selected in next region level.

3. In one example, syntax element equal to (maxNnpfNum-1) may indicates that the NNPF is adaptively selected in next region level.

v. In one example, the signaling of syntax element at current region level may depend on the syntax element at previous (higher) region level.

vi. In one example, area of region A is larger than the area of region B may indicates that level of region A is greater than level of region B and level of region B is lower than level of region A.

1. In one example, picture level is lower than sequence level.

2. In one example, slice level is lower than picture level.

3. In one example, CTU level is lower than slice level.

4. In one example, CU level is lower than CTU level.

5. In one example, CU level is lower than CTU level.

c. One or more syntax elements indicating usage of NNPF at the sequence level may be added into NNPFA SEI message.

i. In one example, syntax element may indicate that NNPF is applied at sequence level or a lower level.

ii. In one example, syntax element at sequence level may be NOT signaled.

d. One or more syntax elements indicating usage of NNPF at the TID level may be added into NNPFA SEI message.

i. In one example, syntax element at TID level may depend on the syntax element at higher level.

ii. In one example, syntax element may indicate that NNPF is applied at TID level or a lower level.

1. In one example, syntax element indicating TID index may be added into NNPFA SEI message.

iii. In one example, syntax element at TID level may be NOT signaled.

e. One or more syntax elements indicating usage of NNPF at the picture level may be added into NNPFA SEI message.

i. In one example, syntax element at picture level may depend on the syn-tax element at higher level.

ii. In one example, syntax element may indicate that NNPF is applied at picture level or a lower level.

iii. In one example, syntax element may indicate that NNPF is applied or not at picture level.

iv. In one example, syntax element may indicate that index of NNPF which is applied at picture level.

v. In one example, syntax element at picture level may be NOT signaled.

f. One or more syntax elements indicating usage of NNPF at the slice level may be added into NNPFA SEI message.

i. In one example, syntax element at slice level may depend on the syntax element at higher level.

ii. In one example, syntax element may indicate that NNPF is applied at slice level or a lower level.

iii. In one example, syntax element at slice level may be NOT signaled.

g. One or more syntax elements indicating usage of NNPF at the sub block/CTU/CTB/patch level may be added into NNPFA SEI message.

i. In one example, syntax element at sub block/CTU/CTB/patch level may depend on the syntax element at higher level (e.g., picture/slice/sequence level) .

ii. In one example, syntax element may indicate that NNPF is applied or not at block/CTU/CTB/patch level.

iii. In one example, syntax element may indicate that index of NNPF which is applied at block/CTU/CTB/patch level.

iv. In one example, syntax element may indicate that NNPF is applied at sub block/CTU/CTB/patch level or a lower level.

v. In one example, syntax element at sub block/CTU/CTB/patch level may be NOT signaled.

h. One or more syntax elements indicating usage of NNPF at the ROI level may be added into NNPFA SEI message.

i. In one example, syntax element at ROI level may depend on the syntax element at higher level.

ii. In one example, syntax element may indicate that NNPF is applied at ROI level or a lower level.

iii. In one example, syntax element at ROI level may be NOT signaled.

i. In one example, the syntax element in NNPFA SEI message may be used for the same video unit/region until meeting a new sequence/SEI.

j. In one example, the syntax element in NNPFA SEI message may be used for the nearest video unit/region.

7) One or more syntax elements indicating improvement/promotion of NNPF may be added into NNPFA and/or NNPFC SEI message.

a. One or more syntax elements indicating performance indicator (or purpose) of NNPF may be added into NNPFA and/or NNPFC SEI message.

i. In one example, purpose may be improving subjective/objective quality.

b. One or more syntax elements indicating performance level of NNPF may be added into NNPFA and/or NNPFC SEI message.

i. In one example, performance level may be normalized value.

ii. In one example, performance level may be different or same for different performance indicator (purpose) .

c. One or more syntax elements indicating complexity level of NNPF may be added into NNPFA and/or NNPFC SEI message.

i. In one example, complexity level may be normalized value.

8) It is proposed that the multiple NNPF and/or characteristics of NNPF may be indicated by adding one or multiple groups of syntax elements into NNPFC SEI message.

a. In one example, one or more syntax elements indicating the number of NNPF may be added into NNPFC SEI message.

i. In one example, the syntax element may be expressed as nnpfc_num_minus1.

1. In one example, the number of NNPF may be equal to nnpfc_num_minus1 + 1.

2. In one example, the value of nnpfc_num_minus1 shall be in the range of 0 to 2^k -1, inclusive.

a. In one example, k may be integer, such as 0,1, 2, 3, 4, 5, 6, 7, …, 32.

ii. In one example, the number of NNPF may be ue (v) -coded.

iii. In one example, the number of NNPF may be smaller than the max value of nnpfc_id plus one.

b. In one example, the number of NNPF may be not signaled into NNPFC SEI message.

i. In one example, the number of NNPF may be set as default value.

ii. In one example, the number of NNPF may be 1, 2, 3, 4, 5.

c. In one example, the number of multiple groups of syntax elements indicating characteristics of NNPF may depend on the number of multiple sets of NNPF.

i. In one example, the number of groups of syntax elements indicating characteristics of NNPF may equal to the number of NNPF.

d. In one example, multiple groups of syntax elements indicating characteristics of NNPF may be signaled for each/all/different NNPF.

i. In one example, every NNPF may have one group of syntax elements indicating characteristics of NNPF.

ii. In one example, multiple groups of syntax elements may be signaled following a certain order.

1. In one example, the group of syntax elements may be signaled one by one.

iii. In one example, i^th group of syntax elements indicating characteristics of NNPF may be used for i^th NNPF.

1. In one example, 1^st group of syntax elements indicating charac-teristics of NNPF may be used for 1^st NNPF.

2. In one example, 2^nd group of syntax elements indicating charac-teristics of NNPF may be used for 2^nd NNPF.

3. In one example, 3^rd group of syntax elements indicating charac-teristics of NNPF may be used for 3^rd NNPF.

iv. In one example, the design of each group of syntax elements may be same.

1. In one example, the number and/or items of each group of syntax elements may be same.

2. In one example, nnpfc_id may be involved in every group of syntax elements.

3. In one example, nnpfc_mode_idc may be involved in every group of syntax elements.

6. Embodiments

Below are some example embodiments for the solution aspects summarized above in Section 5. Most relevant parts that have been added or modified are underlined, and some of the deleted parts are shown inThere may be some other changes that are editorial in nature and thus not highlighted.

6.1. Embodiment 1

6.2. Embodiment 2

6.3. Embodiment 3

6.4. Embodiment 4

6.5. Embodiment 5

6.6. Embodiment 6

More details of the embodiments of the present disclosure will be described below which are related to extension of neural-network post-filter activation and neural-network post-filter characteristics. The embodiments of the present disclosure should be considered as examples to explain the general concepts and should not be interpreted in a narrow way. Furthermore, these embodiments can be applied individually or combined in any manner.

Fig. 10 illustrates a flowchart of a method 1000 for video processing in accordance with some embodiments of the present disclosure. As shown in Fig. 10, at 1002, a conversion between a current video unit of a video and a bitstream of the video is performed. In some embodiments, the conversion may include encoding the current video unit into the bitstream. Alternatively or additionally, the conversion may include decoding the current video unit from the bitstream.

In some embodiments, the bitstream comprises at least one set of syntax elements for activating at least one neural-network post-filter (NNPF) for the current video unit. The current video unit is a portion of a picture of the video. In other words, a level of the current video unit may be lower the picture level. Thereby, the activation of NNPF may be controlled at a level lower than the picture level, such as a slice level, a tile level or the like.

It should be noted that that the terms “activation” , “enabling” , “presence” and “usage” may be used interchangeably herein. For example, the activation of an NNPF may also be referred to as the enabling, the presence or the usage of the NNPF. Moreover, the terms “neural-network post-filter” and “neural-network post-processing filter” may also be used interchangeably.

By way of example rather than limitation, a single NNPF may be activated and used for the current video unit in the current picture, while no NNPF is applied on the rest potion of the current picture. Alternatively, one or more further NNPFs different from the single NNPF is activated and used for the rest portion of the current picture. In a further example, instead of only a single NNPF, a plurality of different NNPFs is activated and used for different portions of the current video unit. Furthermore, the activation of such NNPF (s) may be indicated in the bitstream in aid of one or more sets of syntax elements.

In view of the above, the activation of one or more NNPFs may be controlled at a level lower than the picture level, such as a slice level, a tile level or the like. Compared with the conventional solution, where the activation of one or more NNPFs is controlled at the picture level, the proposed method can advantageously enable the application of NNPF in a refined manner, and thus the coding quality can be improved.

In some embodiments, the at least one set of syntax elements may be comprised in a video message unit in the bitstream. By way of example rather than limitation, the video message unit may be a supplemental enhancement information (SEI) message, such as a neural-network post-filter activation (NNPFA) SEI message or the like. In some embodiments, each set of syntax elements in the at least one set of syntax elements may be represented by SE_activation. It should be understood that the set of syntax elements may also be represented by any other suitable string. The scope of the present disclosure is not limited in this respect.

In some embodiments, a first set of syntax elements in the at least one set of syntax elements may comprise a plurality of syntax elements. In one example, the first set of syntax element may comprise a first syntax element indicating an NNPF specified by one or more neural-network post-filter characteristics (NNPFC) SEI messages that pertain to the picture. By way of example rather than limitation, the first syntax element may be represented by nnpfa_id. It should be understood that the first syntax element may also be represented by any other suitable string. The scope of the present disclosure is not limited in this respect.

Additionally or alternatively, the first set of syntax element may comprise a syntax element indicating the number of the at least one NNPF. In a further example, the first set of syntax element may comprise a syntax element indicating a color component range. As used herein, the color component range may also be referred to as range information or range of color components, or color range. In a still further example, the first set of syntax element may comprise a syntax element indicating a purpose of the color component range. This will be described in detail below.

In some embodiments, the current video unit may comprise a part of a video, a sub-region within the video, a part of a sequence, a sub-region within the sequence, a sub-region within the picture, a slice, a part of the slice, a sub-region within the slice, a tile, a part of the tile, a sub-region within the tile, a brick, a part of the brick, a sub-region within the brick, a subpicture, one or more coding tree units (CTUs) , one or more coding tree blocks (CTBs) , a CTU row, a CTB row, one or more coding units (CUs) , one or more coding blocks (CBs) , or one or more virtual pipeline data units (VPDUs) , or the like.

In some alternative embodiments, the current video unit may comprise a set of patches of the picture. In one example, a patch in the set of patches may be a rectangular array of samples from at least one color component of the picture. By way of example, the at least one color component may comprise a luma component and/or a chroma component. In another example, the at least one color component may comprise a Y component, a U component (Cb component) , and/or a V component (Cr component) . In a further example, the at least one color component may comprise a red (R) component, or a green (G) component, and/or a blue (B) component.

Alternatively, information regarding a patch in the set of patches may be indicated in a video message in the bitstream, such as in the NNPFC SEI message. For example, a width of the patch may be equal to a horizontal sample count of a patch size required for an input to the at least one NNPF, or the width of the patch may be equal to a multiple of the horizontal sample count. The horizontal sample count may be indicated by a syntax element nnpfc_patch_width_minus1. Additionally or alternatively, a height of the patch may be equal to a vertical sample count of a patch size required for an input to the at least one NNPF, or the height of the patch may be equal to a multiple of the vertical sample count. The vertical sample count may be indicated by a syntax element nnpfc_patch_height_minus1.

In some alternative embodiments, the current video unit may comprise a set of regions of the picture. As used herein, a region of a picture may also be referred to as a region of interest (ROI) . For example, one of the set of regions may comprise one or more initial points. Each of the one or more initial points may comprise a horizontal coordinate and a vertical coordinate. Additionally or alternatively, one of the set of regions may comprise one or more ending points. Each of the one or more ending points may comprise a horizontal coordinate and a vertical coordinate. For example, a scope of a region may be determined based on a pair of initial point and ending point. In an additional or alternative example, size information of a region in the set of regions may comprise a width of the region and/or a height of the region.

In some embodiments, a region in the set of regions may be determined based on an output of segmenting a decoded output picture of the video, e.g., according to an image/video segmentation algorithm. In one example, the region may comprise all foreground regions of the decoded output picture. In another example, the region may comprise all background regions of the decoded output picture. In a further example, the region may comprise a type of content (e.g. car, people, cat, sky, etc. ) in the decoded output picture.

In some embodiments, a region in the set of regions may be determined based on an output of applying object classification or object detection on a decoded output picture of the video. In one example, the region may comprise one or more classes of detected objects. Alternatively, the region may comprise a region of the decoded output picture that does not may comprise any detected objects.

In some embodiments, whether the at least one set of syntax elements is applied to a further video unit of the video may be dependent on a relative relationship regarding signaling the further video unit and the video message unit. For example, in a case where the further video unit is signaled after the video message unit, the at least one set of syntax elements may be applied to the further video unit. In a further case where the further video unit is signaled before the video message unit, the at least one set of syntax elements may be applied to the further video unit.

In some embodiments, the at least one set of syntax elements may be dependent on color components and/or a color format of the current video unit. In some embodiments, an NNPFA SEI message in the bitstream may comprise at least one second syntax element indicating a purpose of a color component range. By way of example rather than limitation, the at least one second syntax element may be represented by SE_color_purpose. It should be understood that the at least one second syntax element may also be represented by any other suitable string. The scope of the present disclosure is not limited in this respect.

In some embodiments, a first purpose of the color component range may be that only a single set of syntax elements for activating the at least one NNPF is comprised in an NNPFA SEI message and the activation of the at least one NNPF controlled by the single set of syntax elements is commonly used for one or more color components available to the at least one NNPF. By way of example rather than limitation, the first purpose may be that only one SE_activation need to be involved in NNPFA SEI message and the activation and/or enabling and/or presence and/or usage controlled by SE_activation are commonly used for available color components specified in NNPFC SEI message.

In some embodiments, the one or more color components may be indicated in an NNPFC SEI message or determined based on a design of the at least one NNPF. In some embodiments, a value of one of the at least one second syntax element equal to a first value (e.g., 0 or the like) indicates the first purpose.

In some embodiments, a second purpose of the color component range may be that only a single set of syntax elements for activating the at least one NNPF is comprised in an NNPFA SEI message and the activation of the at least one NNPF controlled by the single set of syntax elements is commonly used for all color components in the color component range. By way of example rather than limitation, the second purpose may be that only one group of SE_activation need to be involved in NNPFA SEI message and the activation and/or enabling and/or presence and/or usage controlled by SE_activation are commonly used for all color components in specified color range. By way of example, a value of one of the at least one second syntax element equal to a second value (e.g., 1 or the like) indicates the second purpose.

In some embodiments, a third purpose of the color component range may be that a plurality of sets of syntax elements for activating the at least one NNPF may be comprised in an NNPFA SEI message and used for different color components in the color component range. By way of example rather than limitation, the third purpose may be that multiple SE_activation need to be involved in NNPFA SEI message and need to be used for different color components in specified color range. By way of example rather than limitation, a value of one of the at least one second syntax element equal to a third value (e.g., 2 or the like) indicates the third purpose.

Alternatively, at least one second syntax element indicating a purpose of color component range may be not comprised in the bitstream. For example, the purpose of the color component range may be predetermined.

In some embodiments, an NNPFA SEI message in the bitstream may comprise at least one third syntax element indicating the color component range. By way of example rather than limitation, the at least one third syntax element may be represented by SE_color_range. It should be understood that the at least one third syntax element may also be represented by any other suitable string. The scope of the present disclosure is not limited in this respect. In some embodiments, the at least one set of syntax elements for activating the at least one NNPF may be used for all color components in the color component range.

In some embodiments, whether to signal the at least one third syntax element may be dependent on the at least one second syntax element. For example. if a value of the at least one second syntax element is equal to a first predetermined value, the at least one third syntax element may be signaled. Moreover, if the value of the at least one second syntax element is equal to a second predetermined value, the at least one third syntax element may be not signaled.

By way of example rather than limitation, when the value of one syntax element of SE_color_purpose equals to 1 or 2 (equivalent to the 2nd purpose or 3rd purpose in the above discussion) the SE_color_range may be signaled. In addition, when the value of one syntax element of SE_color_purpose equals to 0 (equivalent to the 1st purpose in the above discussion) the SE_color_range may be not signaled.

In some embodiments, the at least one set of syntax elements for activating the at least one NNPF may comprise only a single set of syntax elements, and the single set of syntax elements may be commonly used for all color components in the color component range. Alternatively, the at least one set of syntax elements for activating the at least one NNPF may comprise a plurality of sets of syntax elements, and the plurality of sets of syntax elements may be used for different color components in the color component range.

In some embodiments, the number of the plurality of sets of syntax elements may be equal to the number of the different color components. In one example, the color component range may comprise a Y component, a U component, and/or a V component. In another example, the color component range may comprise an R component, or a G component, and/or a B component. For example, the maximum number of color component in the color component range may be 1, 2, or 3.

In some embodiments, the at least one set of syntax elements may comprise one set of syntax elements applied for a plurality of color components. In one example, the plurality of color components may comprise all color components. In another example, the plurality of color components may comprise a Y component, a chroma blue (Cb) component, and/or a chroma red (Cr) component. In a further example, the plurality of color components may comprise an R component, or a G component, and/or a B component. In a still further example, the plurality of color components may comprise chroma components, such as, Cb and Cr components.

In some embodiments, the at least one set of syntax elements may comprise a plurality of sets of syntax elements applied for a plurality of color components separately. For example, the plurality of sets of syntax elements may be applied for all color components separately. In one example, the plurality of sets of syntax elements may comprise a first set of syntax elements applied for a first color component, e.g., a Y component, a Cb component, a Cr component, an R component, a G component or a B component. Additionally, the plurality of sets of syntax elements may comprise a second set of syntax elements applied for a second color component, e.g., a Y component, a Cb component, a Cr component, an R component, a G component or a B component. Furthermore, the plurality of sets of syntax elements may comprise a third set of syntax elements applied for a third color component, e.g., a Y component, a Cb component, a Cr component, an R component, a G component or a B component.

Alternatively, the plurality of sets of syntax elements may be applied for luma and chroma components separately. By way of example, the plurality of sets of syntax elements may comprise a fourth set of syntax elements applied for the luma component. In addition, the plurality of sets of syntax elements may comprise a fifth set of syntax elements applied for the chroma component. Moreover, the fifth set of syntax elements may be the same for Cb and Cr components.

In some embodiments, information regarding whether to and/or how to signal the at least one set of syntax elements may be dependent on the number of the at least one NNPF. In addition, an NNPFA SEI message in the bitstream may comprise a fourth syntax element indicating the number of the at least one NNPF. By way of example rather than limitation, the fourth syntax element may be represented by nnpfa_num_minus1. It should be understood that the fourth syntax element may also be represented by any other suitable string. The scope of the present disclosure is not limited in this respect.

In some embodiments, the number of the at least one NNPF may be equal to a sum of a value of the fourth syntax element and a predetermined value, such as 1 or the like. Furthermore, a value of the fourth syntax element may be in a predetermine range. By way of example, the predetermined range may be from 0 to 2^k-1, and k may be an integer, such as 0, 1, 2, 3, 4, 5, 6, 7, …, 32. It should be understood that the specific value recited here is intended to be exemplary rather than limiting the scope of the present disclosure.

In some embodiments, the fourth syntax element may be ue (v) -coded. That is the fourth syntax element may be an unsigned integer 0-th order Exp-Golomb-coded syntax element with the left bit first. In some embodiments, the number of the at least one NNPF may be smaller than the maximum value of a syntax element nnpfc_id plus one.

In some embodiments, the number of the at least one NNPF may be not indicated in the bitstream. For example, the number of the at least one NNPF may be preset. By way of example rather than limitation, the number of the at least one NNPF may be 1.

In some embodiments, an NNPFA SEI message in the bitstream may comprise at least one fifth syntax element. One of the at least one fifth syntax element indicates an identification of one of the at least one NNPF. By way of example rather than limitation, one of the at least one fifth syntax element may be represented by nnpfa_id. It should be understood that the syntax element may also be represented by any other suitable string. The scope of the present disclosure is not limited in this respect.

In some embodiments, the at least one fifth syntax element may be comprised in the at least one set of syntax elements, e.g., in the SE_activation. In some embodiments, the at least one fifth syntax element may comprise a plurality of fifth syntax elements. Alternatively, the number of the at least one fifth syntax element may be dependent on a color component of the current video unit. Alternatively, the number of the at least one fifth syntax element may be dependent on the number of the at least one NNPF.

In some embodiments, the bitstream may further comprise at least one sixth syntax element indicating a video unit type of the at least one NNPF. As used herein, a video unit type of an NNPF may refer to a type of one or more video units to which the NNPF is applied. For example, the at least one sixth syntax element may be comprised in an NNPFA SEI message and/or an NNPFC SEI message. In addition, the at least one sixth syntax element may be comprised in the at least one set of syntax elements, e.g., in the SE_activation. By way of example, the at least one sixth syntax element may be represented by SE_region_type or nnpfa_region_type. It should be understood that the syntax element may also be represented by any other suitable string. The scope of the present disclosure is not limited in this respect.

In some embodiments, an NNPFA SEI message in the bitstream may comprise at least one seventh syntax element indicating a video unit scope of the at least one NNPF for a corresponding video unit type. The at least one seventh syntax element may be comprised in the at least one set of syntax elements, e.g., in the SE_activation. By way of example rather than limitation, the at least one seventh syntax element may be represented by SE_region_scope. It should be understood that the syntax element may also be represented by any other suitable string. The scope of the present disclosure is not limited in this respect.

In some embodiments, the video unit type may be a region, and the at least one seventh syntax element may be comprised in the at least one set of syntax elements, e.g., in the SE_activation. In some embodiments, the video unit scope may be dependent on the video unit type. In some embodiments, if the video unit type is a predetermined type (such as a picture) , the video unit type may be not indicated in the bitstream. Alternatively, if the video unit type is the predetermined type, the video unit type may be indicated in the bitstream.

In some embodiments, the video unit type may be a sequence, a picture, a slice, a tile, a brick a subpicture, a subregion within the picture, a subregion within the slice, a subregion within the tile, a subregion within the brick, or the like.

In some alternative embodiments, the video unit type may be a CTU. In such a case, an NNPFA SEI message in the bitstream may comprise one or more syntax elements indicating an identification of CTUs to which the at least one NNPF is applied. For example, the identification of CTUs may comprise coordinates of CTUs or a sequence of indexes (such as flags) of CTUs. Alternatively, the video unit type may be a CTB. In such a case, an NNPFA SEI message in the bitstream may comprise one or more syntax elements indicating an identification of CTBs to which the at least one NNPF is applied. For example, the identification of CTBs may comprise coordinates of CTBs, or a sequence of indexes of CTBs.

In some alternative embodiments, the video unit type may be a CTU row. In such a case, an NNPFA SEI message in the bitstream may comprise one or more syntax elements indicating an identification of a CTU row to which the at least one NNPF is applied. For example, the identification of the CTU row may comprise coordinates of the CTU row, or a sequence of indexes of the CTU row. Alternatively, the video unit type may be a CTB row. In such a case, an NNPFA SEI message in the bitstream may comprise one or more syntax elements indicating an identification of a CTB row to which the at least one NNPF is applied. For example, the identification of the CTB row may comprise coordinates of the CTB row, or a sequence of indexes of the CTB row.

In some alternative embodiments, the video unit type may be a CU. In such a case, an NNPFA SEI message in the bitstream may comprise one or more syntax elements indicating an identification of CUs to which the at least one NNPF is applied. For example, the identification of CUs may comprise coordinates of CUs, or a sequence of indexes of CUs. Alternatively, the video unit type may be a CB. In such a case, an NNPFA SEI message in the bitstream may comprise one or more syntax elements indicating an identification of CBs to which the at least one NNPF is applied. For example, the identification of CBs may comprise coordinates of CBs, or a sequence of indexes of CBs.

In some alternative embodiments, the video unit type may be a VPDU. In such a case, an NNPFA SEI message in the bitstream may comprise one or more syntax elements indicating an identification of VPDUs to which the at least one NNPF is applied. For example, the identification of VPDUs may comprise coordinates of VPDUs, or a sequence of indexes of VPDUs.

In some further embodiments, the video unit type may be a patch. In such a case, an NNPFA SEI message in the bitstream may comprise one or more syntax elements indicating a size of a patch to which the at least one NNPF is applied. Additionally or alternatively, the NNPFA SEI message may comprise one or more syntax elements indicating the horizontal number of patches to which the at least one NNPF is applied, the vertical number of the patches, the total number of the patches, and/or the like.

In some alternative embodiments, the video unit type may be a region. In such a case, an NNPFA SEI message in the bitstream may comprise one or more syntax elements indicating an initial point of a region to which the at least one NNPF is applied, an ending point of the region, a width of the region, a height of the region, and/or the like.

In some embodiments, a video unit type of the at least one NNPF may be not indicated in the bitstream. In one example, the video unit type may be preset, such as a picture. In another example, the video unit type has the lowest level. By way of example rather than limitation, the lowest level may be a patch level. In some embodiments, the at least one set of syntax elements may be signaled in an order. For example, a syntax element at a sequence level may be signaled after a syntax element at a picture level.

In some embodiments, an NNPFA SEI message in the bitstream may comprise at least one eighth syntax element indicating an activation of the at least one NNPF. For example, the at least one eighth syntax element may be dependent on a video unit type. By way of example, only syntax elements at a level of a target video unit type may be comprised in the NNPFA SEI message. If the target video unit type is a picture, the NNPFA SEI message may comprise a syntax element indicating the activation of the at least one NNPF at a picture level. If the target video unit type is a slice, the NNPFA SEI message may comprise a syntax element indicating the activation of the at least one NNPF at a slice level. If the target video unit type is a CTU, the NNPFA SEI message may comprise a syntax element indicating the activation of the at least one NNPF at a CTU level.

In some embodiments, an NNPFA SEI message in the bitstream may comprise one or more syntax elements indicating the activation of the at least one NNPF at a video unit level. In one example, syntax elements for different video unit levels may be signaled in an order. By way of example, a syntax element for a first video unit level may be signaled before a syntax element for a second video unit level, and the first video unit level may be higher than the second video unit level. In other words, syntax element of higher video unit level may be signaled before lower video unit level.

In some embodiments, the one or more syntax elements may comprise a ninth syntax element indicating whether the at least one NNPF is used at a current video unit level of the current video unit. By way of example rather than limitation, the ninth syntax element equal to a fourth value (e.g., 0 or the like) indicates that the at least one NNPF is not used at the current video unit level. The ninth syntax element equal to a fifth value (e.g., 1 or the like) indicates that the at least one NNPF is used at the current video unit level. The ninth syntax element greater than the fourth value (e.g., 0 or the like) indicates that the at least one NNPF is used at the current video unit level.

In some embodiments, the one or more syntax elements may comprise a tenth syntax element indicating how to select an NNPF used at a current video unit level of the current video unit or the NNPF used at the current video level. In one example, the tenth syntax element greater than a sixth value (e.g., 0 or the like) indicates that an NNPF with an index equal to a value of the tenth syntax element minus one may be used at the current video unit level. Alternatively, the tenth syntax element smaller than the maximum number of NNPFs indicates that an NNPF with an index equal to a value of the tenth syntax element is used at the current video unit level.

In some embodiments, the one or more syntax elements may comprise an eleventh syntax element indicating whether an NNPF is adaptively selected at a third video unit level lower than a current video unit level of the current video unit. By way of example, the eleventh syntax element equal to a seventh value (e.g., 0 or the like) indicates that the NNPF is adaptively selected at the third video unit level. The eleventh syntax element equal to the maximum number of NNPFs indicates that the NNPF is adaptively selected at the third video unit level. Alternatively, the eleventh syntax element equal to the maximum number of NNPFs minus one indicates that the NNPF is adaptively selected at the third video unit level. By way of example rather than limitation, the maximum number of NNPFs may be denoted as maxNnpfNum.

In some embodiments, the signaling of syntax element at a current video unit level of the current video unit may be dependent on a syntax element at a video unit level higher than the current video unit level. For example, an area of a first video unit being larger than an area of a second video unit indicates that a video unit level of the first video unit is greater than a video unit level of the second video unit. By way of example, a picture level may be lower than a sequence level, a slice level may be lower than the picture level, a CTU level may be lower than the slice level, and a CU level may be lower than the CTU level.

In some embodiments, an NNPFA SEI message in the bitstream may comprise one or more syntax elements indicating the activation of the at least one NNPF at a sequence level. Alternatively, the NNPFA SEI message may comprise a syntax element indicating the activation of the at least one NNPF at a sequence level or a level lower than the sequence level. In some further embodiments, a syntax element indicating the activation of the at least one NNPF at a sequence level may be not indicated in the bitstream.

In some embodiments, an NNPFA SEI message in the bitstream may comprise one or more syntax elements indicating the activation of the at least one NNPF at a temporal layer ID (TID) level. In addition, the one or more syntax elements may be dependent on a syntax element at a level higher than the TID level. Alternatively, the NNPFA SEI message may comprise a syntax element indicating the activation of the at least one NNPF at a TID level or a level lower than the TID level. Moreover, the NNPFA SEI message may further comprise a syntax element indicating an TID index. In some further embodiments, a syntax element indicating the activation of the at least one NNPF at a TID level may be not indicated in the bitstream.

In some embodiments, an NNPFA SEI message in the bitstream may comprise one or more syntax elements indicating the activation of the at least one NNPF at a picture level. Additionally, the one or more syntax elements may be dependent on a syntax element at a level higher than the picture level. In some alternative embodiments, the NNPFA SEI message may comprise a syntax element indicating the activation of the at least one NNPF at a picture level or a level lower than the picture level. Alternatively, the NNPFA SEI message may comprise a syntax element indicating whether the at least one NNPF is activated at a picture level. Furthermore, the NNPFA SEI message may further comprise a syntax element indicating an index of a NNPF applied at the picture level. In some further embodiments, a syntax element indicating the activation of the at least one NNPF at a picture level may be not indicated in the bitstream.

In some embodiments, an NNPFA SEI message in the bitstream may comprise one or more syntax elements indicating the activation of the at least one NNPF at a slice level. In addition, the one or more syntax elements may be dependent on a syntax element at a level higher than the slice level. Alternatively, the NNPFA SEI message may comprise a syntax element indicating the activation of the at least one NNPF at a slice level or a level lower than the slice level. In some further embodiments, a syntax element indicating the activation of the at least one NNPF at a slice level may be not indicated in the bitstream.

In some embodiments, an NNPFA SEI message in the bitstream may comprise one or more syntax elements indicating the activation of the at least one NNPF at a target video unit level. By way of example rather than limitation, the target video unit level may be a sub-block level, a CTU level, a CTB level, a patch level, or the like. Additionally, the one or more syntax elements may be dependent on a syntax element at a level higher than the target video unit level. In some alternative embodiments, the NNPFA SEI message may comprise a syntax element indicating the activation of the at least one NNPF at a target video unit level or a level lower than the target video unit level. In some further embodiments, the NNPFA SEI message may comprise a syntax element indicating whether the at least one NNPF may be activated at a target video unit level. Additionally, the NNPFA SEI message may further comprise a syntax element indicating an index of a NNPF applied at the target video unit level. Alternatively, a syntax element indicating the activation of the at least one NNPF at a target video unit level may be not indicated in the bitstream.

In some embodiments, an NNPFA SEI message in the bitstream may comprise one or more syntax elements indicating the activation of the at least one NNPF at a region level. In addition, the one or more syntax elements may be dependent on a syntax element at a level higher than the region level. Alternatively, an NNPFA SEI message in the bitstream may comprise a syntax element indicating the activation of the at least one NNPF at a region level or a level lower than the region level. In some further embodiments, a syntax element indicating the activation of the at least one NNPF at a region level may be not indicated in the bitstream.

In some embodiments, syntax elements in the NNPFA SEI message may be used for the same video unit or region until meeting a new sequence or SEI message. For example, syntax elements in the NNPFA SEI message may be used for the same video unit or region until a further sequence or a further SEI message is processed. In some additional or alternative embodiments, syntax elements in the NNPFA SEI message may be used for the nearest video unit or region.

In some embodiments, one or more syntax element indicating a quality improvement of the current video unit associated with one of the at least one NNPF may be comprised in at least one of an NNPFA SEI message or an NNPFC SEI message. For example, one or more syntax element indicating a purpose of one of the at least one NNPF may be comprised in at least one of an NNPFA SEI message or an NNPFC SEI message. By way of example rather than limitation, the purpose may comprise improving a subjective quality of the current video unit, improving an objective quality of the current video unit, or the like.

Additionally or alternatively, one or more syntax element indicating a performance level of one of the at least one NNPF may be comprised in at least one of an NNPFA SEI message or an NNPFC SEI message. By way of example rather than limitation, the performance level may be a normalized value. Furthermore, the performance level may be different for different purposes of the NNPC. Alternatively, the performance level may be the same for different purposes of the NNPC.

In some embodiments, one or more syntax element indicating a complexity level of one of the at least one NNPF may be comprised in at least one of an NNPFA SEI message or an NNPFC SEI message. By way of example rather than limitation, the complexity level may be a normalized value.

In some embodiments, an NNPFC SEI message in the bitstream may comprise one or more sets of syntax elements indicating at least one of a plurality of NNPFs or characteristics of NNPF. Additionally, the NNPFC SEI message may comprise a twelfth syntax element indicating the number of the plurality of NNPFs. By way of example, the twelfth syntax element may be represented by nnpfc_num_minus1. It should be understood that the syntax element may also be represented by any other suitable string. The scope of the present disclosure is not limited in this respect.

In some embodiments, the number of the plurality of NNPFs may be equal to a sum of a value of the twelfth syntax element and a predetermined value (e.g., 1 or the like) . Additionally or alternatively, a value of the twelfth syntax element may be in a predetermine range. By way of example, the predetermined range may be from 0 to 2^k-1, and k may be an integer, such as 0, 1, 2, 3, 4, 5, 6, 7, …, 32. In some embodiments, the twelfth syntax element may be ue (v) -coded. That is the twelfth syntax element may be an unsigned integer 0-th order Exp-Golomb-coded syntax element with the left bit first. Alternatively, the number of the plurality of NNPFs may be smaller than the maximum value of a syntax element nnpfc_id plus one.

In some alternative embodiments, the number of the plurality of NNPFs may be not indicated in the bitstream. For example, the number of the plurality of NNPFs may be preset. By way of example rather than limitation, the number of the plurality of NNPFs may be one of 1, 2, 3, 4, or 5.

In some embodiments, the number of the one or more sets of syntax elements may be dependent on the number of the plurality of NNPFs. By way of example, the number of the one or more sets of syntax elements may be equal to the number of the plurality of NNPFs.

In some embodiments, the at least one NNPF may comprise a plurality of NNPFs, and a plurality of sets of syntax elements indicating characteristics of NNPF may be signaled for different NNPFs in the plurality of NNPFs. For example, each of the at least one NNPF may be associated with a set of syntax elements indicating characteristics of NNPF. In one example, the plurality of sets of syntax elements may be signaled in an order. Additionally or alternatively, the plurality of sets of syntax elements may be signaled one by one.

In some embodiments, an i-th set of syntax element in the plurality of sets of syntax elements may be used for an i-th NNPFs of the plurality of NNPFs, where i may be an integer, such as 1, 2, 3, or the like.

In some embodiments, a design of each set of syntax elements in the plurality of sets of syntax elements may be the same. For example, the number of syntax elements in each set of syntax elements among the plurality of sets of syntax elements may be the same. Additionally or alternatively, syntax elements in each set of syntax elements among the plurality of sets of syntax elements may be the same.

In some embodiments, each set of syntax elements in the plurality of sets of syntax elements may comprise a thirteenth syntax element indicating an identifying number of an NNPF. For example, the thirteenth syntax element may be represented by nnpfc_id. It should be understood that the thirteenth syntax element may also be represented by any other suitable string. The scope of the present disclosure is not limited in this respect.

In some embodiments, each set of syntax elements in the plurality of sets of syntax elements may comprise a fourteenth syntax element indicating how to obtain an NNPF associated with a value of the thirteenth syntax element. In one example, the fourteenth syntax element may be represented by nnpfc_mode_idc. It should be understood that the fourteenth syntax element may also be represented by any other suitable string. The scope of the present disclosure is not limited in this respect.

According to further embodiments of the present disclosure, a non-transitory computer-readable recording medium is provided. The non-transitory computer-readable recording medium stores a bitstream of a video which is generated by a method performed by an apparatus for video processing. In the method, a conversion between a current video unit of the video and the bitstream is performed. The bitstream comprises at least one set of syntax elements for activating at least one NNPF for the current video unit, and the current video unit is a portion of a picture of the video.

According to still further embodiments of the present disclosure, a method for storing bitstream of a video is provided. According to the method, a conversion between a current video unit of the video and the bitstream is performed. The bitstream comprises at least one set of syntax elements for activating at least one NNPF for the current video unit, and the current video unit is a portion of a picture of the video. Moreover, the bitstream is stored in a non-transitory computer-readable recording medium.

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

Clause 1. A method for video processing, comprising: performing a conversion between a current video unit of a video and a bitstream of the video, wherein the bitstream comprises at least one set of syntax elements for activating at least one neural-network post-filter (NNPF) for the current video unit, and the current video unit is a portion of a picture of the video.

Clause 2. The method of clause 1, wherein the at least one set of syntax elements is comprised in a video message unit in the bitstream.

Clause 3. The method of clause 2, wherein the video message unit is a supplemental enhancement information (SEI) message.

Clause 4. The method of clause 2, wherein the video message unit is a neural-network post-filter activation (NNPFA) SEI message.

Clause 5. The method of any of clauses 1-4, wherein each set of syntax elements in the at least one set of syntax elements is represented by SE_activation.

Clause 6. The method of any of clauses 1-5, wherein a first set of syntax elements in the at least one set of syntax elements comprises a plurality of syntax elements.

Clause 7. The method of clause 6, wherein the first set of syntax element comprises a first syntax element indicating an NNPF specified by one or more neural-network post-filter characteristics (NNPFC) SEI messages that pertain to the picture.

Clause 8. The method of clause 7, wherein the first syntax element is represented by nnpfa_id.

Clause 9. The method of any of clauses 6-8, wherein the first set of syntax element comprises a syntax element indicating the number of the at least one NNPF.

Clause 10. The method of any of clauses 6-9, wherein the first set of syntax element comprises a syntax element indicating a color component range.

Clause 11. The method of any of clauses 6-10, wherein the first set of syntax element comprises a syntax element indicating a purpose of the color component range.

Clause 12. The method of any of clauses 1-11, wherein the current video unit comprises one of the following: a part of a video, a sub-region within the video, a part of a sequence, a sub-region within the sequence, a sub-region within the picture, a slice, a part of the slice, a sub-region within the slice, a tile, a part of the tile, a sub-region within the tile, a brick, a part of the brick, a sub-region within the brick, a subpicture, one or more coding tree units (CTUs) , one or more coding tree blocks (CTBs) , a CTU row, a CTB row, one or more coding units (CUs) , one or more coding blocks (CBs) , or one or more virtual pipeline data units (VPDUs) .

Clause 13. The method of any of clauses 1-11, wherein the current video unit comprises a set of patches of the picture.

Clause 14. The method of clause 13, wherein one of the set of patches is a rectangular array of samples from at least one color component of the picture.

Clause 15. The method of clause 14, wherein the at least one color component comprises at least one of the following: a luma component, or a chroma component.

Clause 16. The method of clause 14, wherein the at least one color component comprises at least one of the following: a Y component, a U component, or a V component.

Clause 17. The method of clause 14, wherein the at least one color component comprises at least one of the following: a red (R) component, or a green (G) component, or a blue (B) component.

Clause 18. The method of clause 13, wherein information regarding a patch in the set of patches is indicated in a video message in the bitstream.

Clause 19. The method of clause 18, wherein the video message is an NNPFC SEI message.

Clause 20. The method of any of clauses 18-19, wherein a width of the patch is equal to a horizontal sample count of a patch size required for an input to the at least one NNPF, or the width of the patch is equal to a multiple of the horizontal sample count.

Clause 21. The method of clause 20, wherein the horizontal sample count is indicated by a syntax element nnpfc_patch_width_minus1.

Clause 22. The method of any of clauses 18-21, wherein a height of the patch is equal to a vertical sample count of a patch size required for an input to the at least one NNPF, or the height of the patch is equal to a multiple of the vertical sample count.

Clause 23. The method of clause 22, wherein the vertical sample count is indicated by a syntax element nnpfc_patch_height_minus1.

Clause 24. The method of any of clauses 1-11, wherein the current video unit comprises a set of regions of the picture.

Clause 25. The method of clause 24, wherein one of the set of regions comprises one or more initial points.

Clause 26. The method of clause 25, wherein each of the one or more initial points comprise a horizontal coordinate and a vertical coordinate.

Clause 27. The method of any of clauses 24-26, wherein one of the set of regions comprises one or more ending points.

Clause 28. The method of clause 27, wherein each of the one or more ending points comprise a horizontal coordinate and a vertical coordinate.

Clause 29. The method of any of clauses 24-28, wherein size information of a region in the set of regions comprises at least one of the following: a width of the region, or a height of the region.

Clause 30. The method of clause 24, wherein a region in the set of regions is determined based on an output of segmenting a decoded output picture of the video.

Clause 31. The method of clause 30, wherein the region comprises one of the following: all foreground regions of the decoded output picture, all background regions of the decoded output picture, or a type of content in the decoded output picture.

Clause 32. The method of clause 24, wherein a region in the set of regions is determined based on an output of applying object classification or object detection on a decoded output picture of the video.

Clause 33. The method of clause 32, wherein the region comprises one or more classes of detected objects.

Clause 34. The method of clause 32, wherein the region comprises a region of the decoded output picture that does not comprise any detected objects.

Clause 35. The method of any of clauses 2-34, wherein whether the at least one set of syntax elements is applied to a further video unit of the video is dependent on a relative relationship regarding signaling the further video unit and the video message unit.

Clause 36. The method of clause 35, wherein the further video unit is signaled after the video message unit, and the at least one set of syntax elements is applied to the further video unit.

Clause 37. The method of clause 35, wherein the further video unit is signaled before the video message unit, and the at least one set of syntax elements is applied to the further video unit.

Clause 38. The method of any of clauses 1-37, wherein the at least one set of syntax elements is dependent on at least one of color components or a color format of the current video unit.

Clause 39. The method of any of clauses 1-38, wherein an NNPFA SEI message in the bitstream comprises at least one second syntax element indicating a purpose of a color component range.

Clause 40. The method of clause 39, wherein the at least one second syntax element is represented by SE_color_purpose.

Clause 41. The method of any of clauses 39-40, wherein a first purpose of the color component range is that only a single set of syntax elements for activating the at least one NNPF is comprised in an NNPFA SEI message and the activation of the at least one NNPF controlled by the single set of syntax elements is commonly used for one or more color components available to the at least one NNPF.

Clause 42. The method of clause 41, wherein the one or more color components is indicated in an NNPFC SEI message or determined based on a design of the at least one NNPF.

Clause 43. The method of any of clauses 41-42, wherein a value of one of the at least one second syntax element equal to a first value indicates the first purpose.

Clause 44. The method of clause 43, wherein the first value is 0.

Clause 45. The method of any of clauses 39-44, wherein a second purpose of the color component range is that only a single set of syntax elements for activating the at least one NNPF is comprised in an NNPFA SEI message and the activation of the at least one NNPF controlled by the single set of syntax elements is commonly used for all color components in the color component range.

Clause 46. The method of clause 45, wherein a value of one of the at least one second syntax element equal to a second value indicates the second purpose.

Clause 47. The method of clause 46, wherein the second value is 1.

Clause 48. The method of any of clauses 39-47, wherein a third purpose of the color component range is that a plurality of sets of syntax elements for activating the at least one NNPF are comprised in an NNPFA SEI message and used for different color components in the color component range.

Clause 49. The method of clause 48, wherein a value of one of the at least one second syntax element equal to a third value indicates the third purpose.

Clause 50. The method of clause 49, wherein the third value is 2.

Clause 51. The method of any of clauses 1-38, wherein at least one second syntax element indicating a purpose of color component range is not comprised in the bitstream.

Clause 52. The method of clause 51, wherein the purpose of the color component range is predetermined.

Clause 53. The method of any of clauses 39-52, wherein an NNPFA SEI message in the bitstream comprises at least one third syntax element indicating the color component range.

Clause 54. The method of clause 53, wherein the at least one third syntax element is represented by SE_color_range.

Clause 55. The method of any of clauses 53-54, wherein the at least one set of syntax elements for activating the at least one NNPF is used for all color components in the color component range.

Clause 56. The method of any of clauses 53-55, wherein whether to signal the at least one third syntax element is dependent on the at least one second syntax element.

Clause 57. The method of clause 56, wherein if a value of the at least one second syntax element is equal to a first predetermined value, the at least one third syntax element is signaled, and if the value of the at least one second syntax element is equal to a second predetermined value, the at least one third syntax element is not signaled.

Clause 58. The method of clause 55, wherein the at least one set of syntax elements for activating the at least one NNPF comprises only a single set of syntax elements, and the single set of syntax elements is commonly used for all color components in the color component range.

Clause 59. The method of clause 55, wherein the at least one set of syntax elements for activating the at least one NNPF comprises a plurality of sets of syntax elements, and the plurality of sets of syntax elements are used for different color components in the color component range.

Clause 60. The method of clause 59, wherein the number of the plurality of sets of syntax elements is equal to the number of the different color components.

Clause 61. The method of any of clauses 39-60, wherein the color component range comprises at least one of the following: a Y component, a U component, or a V component.

Clause 62. The method of any of clauses 39-60, wherein the color component range comprises at least one of the following: an R component, or a G component, or a B component.

Clause 63. The method of any of clauses 39-62, wherein the maximum number of color component in the color component range is 1, 2, or 3.

Clause 64. The method of any of clauses 1-63, wherein the at least one set of syntax elements comprises one set of syntax elements applied for a plurality of color components.

Clause 65. The method of clause 64, wherein the plurality of color components comprise all color components.

Clause 66. The method of clause 64, wherein the plurality of color components comprise at least one of the following: a Y component, a chroma blue (Cb) component, or a chroma red (Cr) component.

Clause 67. The method of clause 64, wherein the plurality of color components comprise at least one of the following: an R component, or a G component, or a B component.

Clause 68. The method of clause 64, wherein the plurality of color components comprise chroma components.

Clause 69. The method of clause 64, wherein the plurality of color components comprise Cb and Cr components.

Clause 70. The method of any of clauses 1-63, wherein the at least one set of syntax elements comprises a plurality of sets of syntax elements applied for a plurality of color components separately.

Clause 71. The method of clause 70, wherein the plurality of sets of syntax elements are applied for all color components separately.

Clause 72. The method of clause 71, wherein the plurality of sets of syntax elements comprise a first set of syntax elements applied for a first color component.

Clause 73. The method of clause 72, wherein the first color component is one of a Y component, a Cb component, a Cr component, an R component, a G component or a B component.

Clause 74. The method of any of clauses 71-73, wherein the plurality of sets of syntax elements comprise a second set of syntax elements applied for a second color component.

Clause 75. The method of clause 74, wherein the second color component is one of a Y component, a Cb component, a Cr component, an R component, a G component or a B component.

Clause 76. The method of any of clauses 71-75, wherein the plurality of sets of syntax elements comprise a third set of syntax elements applied for a third color component.

Clause 77. The method of clause 76, wherein the third color component is one of a Y component, a Cb component, a Cr component, an R component, a G component or a B component.

Clause 78. The method of clause 70, wherein the plurality of sets of syntax elements are applied for luma and chroma components separately.

Clause 79. The method of clause 78, wherein the plurality of sets of syntax elements comprises a fourth set of syntax elements applied for the luma component.

Clause 80. The method of clause 79, wherein the plurality of sets of syntax elements comprises a fifth set of syntax elements applied for the chroma component.

Clause 81. The method of clause 80, wherein the fifth set of syntax elements are the same for Cb and Cr components.

Clause 82. The method of any of clauses 1-81, wherein information regarding whether to and/or how to signal the at least one set of syntax elements is dependent on the number of the at least one NNPF.

Clause 83. The method of clause 82, wherein an NNPFA SEI message in the bitstream comprises a fourth syntax element indicating the number of the at least one NNPF.

Clause 84. The method of clause 83, wherein the fourth syntax element is represented by nnpfa_num_minus1.

Clause 85. The method of any of clauses 83-84, wherein the number of the at least one NNPF is equal to a sum of a value of the fourth syntax element and a predetermined value.

Clause 86. The method of any of clauses 83-85, wherein a value of the fourth syntax element is in a predetermine range.

Clause 87. The method of clause 86, wherein the predetermined range is from 0 to 2^k-1, and k is an integer.

Clause 88. The method of any of clauses 83-87, wherein the fourth syntax element is an unsigned integer 0-th order Exp-Golomb-coded syntax element with the left bit first.

Clause 89. The method of any of clauses 1-88, wherein the number of the at least one NNPF is smaller than the maximum value of a syntax element nnpfc_id plus one.

Clause 90. The method of any of clauses 1-82, wherein the number of the at least one NNPF is not indicated in the bitstream.

Clause 91. The method of clause 90, wherein the number of the at least one NNPF is preset.

Clause 92. The method of any of clauses 90-91, wherein the number of the at least one NNPF is 1.

Clause 93. The method of any of clauses 1-92, wherein an NNPFA SEI message in the bitstream comprises at least one fifth syntax element, and one of the at least one fifth syntax element indicates an identification of one of the at least one NNPF.

Clause 94. The method of clause 93, wherein one of the at least one fifth syntax element is represented by nnpfa_id.

Clause 95. The method of any of clauses 93-94, wherein the at least one fifth syntax element is comprised in the at least one set of syntax elements.

Clause 96. The method of any of clauses 93-95, wherein the at least one fifth syntax element comprises a plurality of fifth syntax elements.

Clause 97. The method of any of clauses 93-96, wherein the number of the at least one fifth syntax element is dependent on a color component of the current video unit.

Clause 98. The method of any of clauses 93-97, wherein the number of the at least one fifth syntax element is dependent on the number of the at least one NNPF.

Clause 99. The method of any of clauses 1-98, wherein the bitstream further comprises at least one sixth syntax element indicating a video unit type of the at least one NNPF.

Clause 100. The method of clause 99, wherein the at least one sixth syntax element is comprised in at least one of the following: an NNPFA SEI message, or an NNPFC SEI message.

Clause 101. The method of any of clauses 99-100, wherein the at least one sixth syntax element is comprised in the at least one set of syntax elements.

Clause 102. The method of any of clauses 99-101, wherein the at least one sixth syntax element is represented by SE_region_type or nnpfa_region_type.

Clause 103. The method of any of clauses 99-102, wherein an NNPFA SEI message in the bitstream comprises at least one seventh syntax element indicating a video unit scope of the at least one NNPF for a corresponding video unit type.

Clause 104. The method of clause 103, wherein the at least one seventh syntax element is represented by SE_region_scope.

Clause 105. The method of any of clauses 103-104, wherein the at least one seventh syntax element is comprised in the at least one set of syntax elements.

Clause 106. The method of any of clauses 103-104, wherein the video unit type is a region, and the at least one seventh syntax element is comprised in the at least one set of syntax elements.

Clause 107. The method of any of clauses 103-106, wherein the video unit scope is dependent on the video unit type.

Clause 108. The method of any of clauses 103-107, wherein if the video unit type is a predetermined type, the video unit type is not indicated in the bitstream.

Clause 109. The method of any of clauses 103-107, wherein if the video unit type is a predetermined type, the video unit type is indicated in the bitstream.

Clause 110. The method of any of clauses 108-109, wherein the predetermined type is a picture.

Clause 111. The method of any of clauses 99-110, wherein the video unit type is one of the following: a sequence, a picture, a slice, a tile, a brick a subpicture, a subregion within the picture, a subregion within the slice, a subregion within the tile, or a subregion within the brick.

Clause 112. The method of any of clauses 99-110, wherein the video unit type is a CTU.

Clause 113. The method of clause 112, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating an identification of CTUs to which the at least one NNPF is applied.

Clause 114. The method of clause 113, wherein the identification of CTUs comprises coordinates of CTUs, or a sequence of indexes of CTUs.

Clause 115. The method of any of clauses 99-110, wherein the video unit type is a CTB.

Clause 116. The method of clause 115, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating an identification of CTBs to which the at least one NNPF is applied.

Clause 117. The method of clause 116, wherein the identification of CTBs comprises coordinates of CTBs, or a sequence of indexes of CTBs.

Clause 118. The method of any of clauses 99-110, wherein the video unit type is a CTU row.

Clause 119. The method of clause 118, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating an identification of a CTU row to which the at least one NNPF is applied.

Clause 120. The method of clause 119, wherein the identification of the CTU row comprises coordinates of the CTU row, or a sequence of indexes of the CTU row.

Clause 121. The method of any of clauses 99-110, wherein the video unit type is a CTB row.

Clause 122. The method of clause 121, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating an identification of a CTB row to which the at least one NNPF is applied.

Clause 123. The method of clause 122, wherein the identification of the CTB row comprises coordinates of the CTB row, or a sequence of indexes of the CTB row.

Clause 124. The method of any of clauses 99-110, wherein the video unit type is a CU.

Clause 125. The method of clause 124, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating an identification of CUs to which the at least one NNPF is applied.

Clause 126. The method of clause 125, wherein the identification of CUs comprises coordinates of CUs, or a sequence of indexes of CUs.

Clause 127. The method of any of clauses 99-110, wherein the video unit type is a CB.

Clause 128. The method of clause 127, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating an identification of CBs to which the at least one NNPF is applied.

Clause 129. The method of clause 128, wherein the identification of CBs comprises coordinates of CBs, or a sequence of indexes of CBs.

Clause 130. The method of any of clauses 99-110, wherein the video unit type is a VPDU.

Clause 131. The method of clause 131, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating an identification of VPDUs to which the at least one NNPF is applied.

Clause 132. The method of clause 131, wherein the identification of VPDUs comprises coordinates of VPDUs, or a sequence of indexes of VPDUs.

Clause 133. The method of any of clauses 99-110, wherein the video unit type is a patch.

Clause 134. The method of clause 133, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating a size of a patch to which the at least one NNPF is applied.

Clause 135. The method of any of clauses 133-134, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating at least one of the following: the horizontal number of patches to which the at least one NNPF is applied, the vertical number of the patches, or the total number of the patches.

Clause 136. The method of any of clauses 99-110, wherein the video unit type is a region.

Clause 137. The method of clause 136, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating at least one of the following: an initial point of a region to which the at least one NNPF is applied, an ending point of the region, a width of the region, or a height of the region.

Clause 138. The method of any of clauses 1-98, wherein a video unit type of the at least one NNPF is not indicated in the bitstream.

Clause 139. The method of clause 138, wherein the video unit type is preset.

Clause 140. The method of any of clauses 138-139, wherein the video unit type is a picture.

Clause 141. The method of any of clauses 138-139, wherein the video unit type has the lowest level.

Clause 142. The method of clause 141, wherein the lowest level is a patch level.

Clause 143. The method of any of clauses 138-142, wherein the at least one set of syntax elements are signaled in an order.

Clause 144. The method of clause 143, wherein a syntax element at a sequence level is signaled after a syntax element at a picture level.

Clause 145. The method of any of clauses 1-144, wherein an NNPFA SEI message in the bitstream comprises at least one eighth syntax element indicating an activation of the at least one NNPF.

Clause 146. The method of clause 145, wherein the at least one eighth syntax element is dependent on a video unit type.

Clause 147. The method of clause 146, wherein only syntax elements at a level of a target video unit type are comprised in the NNPFA SEI message.

Clause 148. The method of clause 147, wherein if the target video unit type is a picture, the NNPFA SEI message comprises a syntax element indicating the activation of the at least one NNPF at a picture level, or if the target video unit type is a slice, the NNPFA SEI message comprises a syntax element indicating the activation of the at least one NNPF at a slice level, or if the target video unit type is a CTU, the NNPFA SEI message comprises a syntax element indicating the activation of the at least one NNPF at a CTU level.

Clause 149. The method of any of clauses 1-144, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating the activation of the at least one NNPF at a video unit level.

Clause 150. The method of clause 149, wherein syntax elements for different video unit levels are signaled in an order.

Clause 151. The method of clause 150, wherein a syntax element for a first video unit level is signaled before a syntax element for a second video unit level, and the first video unit level is higher than the second video unit level.

Clause 152. The method of any of clauses 149-151, wherein the one or more syntax elements comprises a ninth syntax element indicating whether the at least one NNPF is used at a current video unit level of the current video unit.

Clause 153. The method of clause 152, wherein the ninth syntax element equal to a fourth value indicates that the at least one NNPF is not used at the current video unit level, or the ninth syntax element equal to a fifth value indicates that the at least one NNPF is used at the current video unit level, or the ninth syntax element greater than the fourth value indicates that the at least one NNPF is used at the current video unit level.

Clause 154. The method of clause 153, wherein the fourth value is 0 or the fifth value is 1.

Clause 155. The method of any of clauses 149-154, wherein the one or more syntax elements comprises a tenth syntax element indicating one of the following: how to select an NNPF used at a current video unit level of the current video unit, or the NNPF used at the current video level.

Clause 156. The method of clause 155, wherein the tenth syntax element greater than a sixth value indicates that an NNPF with an index equal to a value of the tenth syntax element minus one is used at the current video unit level.

Clause 157. The method of clause 156, wherein the sixth value is 0.

Clause 158. The method of clause 155, wherein the tenth syntax element smaller than the maximum number of NNPFs indicates that an NNPF with an index equal to a value of the tenth syntax element is used at the current video unit level.

Clause 159. The method of any of clauses 149-158, wherein the one or more syntax elements comprises an eleventh syntax element indicating whether an NNPF is adaptively selected at a third video unit level lower than a current video unit level of the current video unit.

Clause 160. The method of clause 159, wherein the eleventh syntax element equal to a seventh value indicates that the NNPF is adaptively selected at the third video unit level, or the eleventh syntax element equal to the maximum number of NNPFs indicates that the NNPF is adaptively selected at the third video unit level, or the eleventh syntax element equal to the maximum number of NNPFs minus one indicates that the NNPF is adaptively selected at the third video unit level.

Clause 161. The method of clause 160, wherein the seventh value is 0.

Clause 162. The method of any of clauses 149-161, wherein signaling of syntax element at a current video unit level of the current video unit is dependent on a syntax element at a video unit level higher than the current video unit level.

Clause 163. The method of any of clauses 149-162, wherein an area of a first video unit being larger than an area of a second video unit indicates that a video unit level of the first video unit is greater than a video unit level of the second video unit.

Clause 164. The method of any of clauses 149-163, wherein a picture level is lower than a sequence level, a slice level is lower than the picture level, a CTU level is lower than the slice level, and a CU level is lower than the CTU level.

Clause 165. The method of any of clauses 1-164, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating the activation of the at least one NNPF at a sequence level.

Clause 166. The method of any of clauses 1-164, wherein an NNPFA SEI message in the bitstream comprises a syntax element indicating the activation of the at least one NNPF at a sequence level or a level lower than the sequence level.

Clause 167. The method of any of clauses 1-164, wherein a syntax element indicating the activation of the at least one NNPF at a sequence level is not indicated in the bitstream.

Clause 168. The method of any of clauses 1-167, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating the activation of the at least one NNPF at a temporal layer ID (TID) level.

Clause 169. The method of clause 168, wherein the one or more syntax elements are dependent on a syntax element at a level higher than the TID level.

Clause 170. The method of any of clauses 1-167, wherein an NNPFA SEI message in the bitstream comprises a syntax element indicating the activation of the at least one NNPF at a TID level or a level lower than the TID level.

Clause 171. The method of clause 170, wherein the NNPFA SEI message further comprises a syntax element indicating an TID index.

Clause 172. The method of any of clauses 1-167, wherein a syntax element indicating the activation of the at least one NNPF at a TID level is not indicated in the bitstream.

Clause 173. The method of any of clauses 1-172, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating the activation of the at least one NNPF at a picture level.

Clause 174. The method of clause 173, wherein the one or more syntax elements are dependent on a syntax element at a level higher than the picture level.

Clause 175. The method of any of clauses 1-172, wherein an NNPFA SEI message in the bitstream comprises a syntax element indicating the activation of the at least one NNPF at a picture level or a level lower than the picture level.

Clause 176. The method of any of clauses 1-172, wherein an NNPFA SEI message in the bitstream comprises a syntax element indicating whether the at least one NNPF is activated at a picture level.

Clause 177. The method of any of clauses 173-176, wherein the NNPFA SEI message further comprises a syntax element indicating an index of a NNPF applied at the picture level.

Clause 178. The method of any of clauses 1-172, wherein a syntax element indicating the activation of the at least one NNPF at a picture level is not indicated in the bitstream.

Clause 179. The method of any of clauses 1-178, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating the activation of the at least one NNPF at a slice level.

Clause 180. The method of clause 179, wherein the one or more syntax elements are dependent on a syntax element at a level higher than the slice level.

Clause 181. The method of any of clauses 1-178, wherein an NNPFA SEI message in the bitstream comprises a syntax element indicating the activation of the at least one NNPF at a slice level or a level lower than the slice level.

Clause 182. The method of any of clauses 1-178, wherein a syntax element indicating the activation of the at least one NNPF at a slice level is not indicated in the bitstream.

Clause 183. The method of any of clauses 1-182, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating the activation of the at least one NNPF at a target video unit level.

Clause 184. The method of clause 183, wherein the one or more syntax elements are dependent on a syntax element at a level higher than the target video unit level.

Clause 185. The method of any of clauses 1-182, wherein an NNPFA SEI message in the bitstream comprises a syntax element indicating the activation of the at least one NNPF at a target video unit level or a level lower than the target video unit level.

Clause 186. The method of any of clauses 1-182, wherein an NNPFA SEI message in the bitstream comprises a syntax element indicating whether the at least one NNPF is activated at a target video unit level.

Clause 187. The method of any of clauses 183-186, wherein the NNPFA SEI message further comprises a syntax element indicating an index of a NNPF applied at the target video unit level.

Clause 188. The method of any of clauses 1-182, wherein a syntax element indicating the activation of the at least one NNPF at a target video unit level is not indicated in the bitstream.

Clause 189. The method of any of clauses 182-188, wherein the target video unit level is one of the following: a sub-block level, a CTU level, a CTB level, or a patch level.

Clause 190. The method of any of clauses 1-189, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating the activation of the at least one NNPF at a region level.

Clause 191. The method of clause 190, wherein the one or more syntax elements are dependent on a syntax element at a level higher than the region level.

Clause 192. The method of any of clauses 1-189, wherein an NNPFA SEI message in the bitstream comprises a syntax element indicating the activation of the at least one NNPF at a region level or a level lower than the region level.

Clause 193. The method of any of clauses 1-189, wherein a syntax element indicating the activation of the at least one NNPF at a region level is not indicated in the bitstream.

Clause 194. The method of any of clauses 145-193, wherein syntax elements in the NNPFA SEI message are used for the same video unit or region until a further sequence or a further SEI message is processed.

Clause 195. The method of any of clauses 145-193, wherein syntax elements in the NNPFA SEI message are used for the nearest video unit or region.

Clause 196. The method of any of clauses 1-195, wherein one or more syntax element indicating a quality improvement of the current video unit associated with one of the at least one NNPF is comprised in at least one of an NNPFA SEI message or an NNPFC SEI message.

Clause 197. The method of any of clauses 1-196, wherein one or more syntax element indicating a purpose of one of the at least one NNPF is comprised in at least one of an NNPFA SEI message or an NNPFC SEI message.

Clause 198. The method of clause 197, wherein the purpose comprises improving a subjective quality of the current video unit or improving an objective quality of the current video unit.

Clause 199. The method of clause 1-198, wherein one or more syntax element indicating a performance level of one of the at least one NNPF is comprised in at least one of an NNPFA SEI message or an NNPFC SEI message.

Clause 200. The method of clause 199, wherein the performance level is a normalized value.

Clause 201. The method of clause 199, wherein the performance level is different for different purposes of the NNPC, or the performance level is the same for different purposes of the NNPC.

Clause 202. The method of clause 1-201, wherein one or more syntax element indicating a complexity level of one of the at least one NNPF is comprised in at least one of an NNPFA SEI message or an NNPFC SEI message.

Clause 203. The method of clause 202, wherein the complexity level is a normalized value.

Clause 204. The method of any of clauses 1-203, wherein an NNPFC SEI message in the bitstream comprises one or more sets of syntax elements indicating at least one of a plurality of NNPFs or characteristics of NNPF.

Clause 205. The method of clause 204, wherein the NNPFC SEI message comprises a twelfth syntax element indicating the number of the plurality of NNPFs.

Clause 206. The method of clause 205, wherein the twelfth syntax element is represented by nnpfc_num_minus1.

Clause 207. The method of any of clauses 205-206, wherein the number of the plurality of NNPFs is equal to a sum of a value of the twelfth syntax element and a predetermined value.

Clause 208. The method of any of clauses 205-207, wherein a value of the twelfth syntax element is in a predetermine range.

Clause 209. The method of clause 208, wherein the predetermined range is from 0 to 2^k-1, and k is an integer.

Clause 210. The method of any of clauses 205-209, wherein the twelfth syntax element is an unsigned integer 0-th order Exp-Golomb-coded syntax element with the left bit first.

Clause 211. The method of any of clauses 1-210, wherein the number of the plurality of NNPFs is smaller than the maximum value of a syntax element nnpfc_id plus one.

Clause 212. The method of clause 204, wherein the number of the plurality of NNPFs is not indicated in the bitstream.

Clause 213. The method of clause 212, wherein the number of the plurality of NNPFs is preset.

Clause 214. The method of any of clauses 212-213, wherein the number of the plurality of NNPFs is one of 1, 2, 3, 4, or 5.

Clause 215. The method of any of clauses 204-214, wherein the number of the one or more sets of syntax elements is dependent on the number of the plurality of NNPFs.

Clause 216. The method of clause 215, wherein the number of the one or more sets of syntax elements is equal to the number of the plurality of NNPFs.

Clause 217. The method of any of clauses 1-203, wherein the at least one NNPF comprises a plurality of NNPFs, and a plurality of sets of syntax elements indicating characteristics of NNPF are signaled for different NNPFs in the plurality of NNPFs.

Clause 218. The method of clause 217, wherein each of the at least one NNPF is associated with a set of syntax elements indicating characteristics of NNPF.

Clause 219. The method of clause 217, wherein the plurality of sets of syntax elements are signaled in an order.

Clause 220. The method of clause 217, wherein the plurality of sets of syntax elements are signaled one by one.

Clause 221. The method of any of clauses 217-220, wherein an i-th set of syntax element in the plurality of sets of syntax elements is used for an i-th NNPFs of the plurality of NNPFs, where i is an integer.

Clause 222. The method of clause 221, wherein i is 1, 2, or 3.

Clause 223. The method of any of clauses 217-222, wherein a design of each set of syntax elements in the plurality of sets of syntax elements is the same.

Clause 224. The method of any of clauses 217-222, wherein at least one of the following is the same: the number of syntax elements in each set of syntax elements among the plurality of sets of syntax elements, or syntax elements in each set of syntax elements among the plurality of sets of syntax elements.

Clause 225. The method of any of clauses 217-222, wherein each set of syntax elements in the plurality of sets of syntax elements comprises a thirteenth syntax element indicating an identifying number of an NNPF.

Clause 226. The method of clause 225, wherein the thirteenth syntax element is represented by nnpfc_id.

Clause 227. The method of any of clauses 225-226, wherein each set of syntax elements in the plurality of sets of syntax elements comprises a fourteenth syntax element indicating how to obtain an NNPF associated with a value of the thirteenth syntax element.

Clause 228. The method of clause 227, wherein the fourteenth syntax element is represented by nnpfc_mode_idc.

Clause 229. The method of any of clauses 1-228, wherein the conversion includes encoding the current video unit into the bitstream.

Clause 230. The method of any of clauses 1-228, wherein the conversion includes decoding the current video unit from the bitstream.

Clause 231. An apparatus for video processing comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to perform a method in accordance with any of clauses 1-230.

Clause 232. A non-transitory computer-readable storage medium storing instructions that cause a processor to perform a method in accordance with any of clauses 1-230.

Clause 233. A non-transitory computer-readable recording medium storing a bitstream of a video which is generated by a method performed by an apparatus for video processing, wherein the method comprises: performing a conversion between a current video unit of the video and the bitstream, wherein the bitstream comprises at least one set of syntax elements for activating at least one neural-network post-filter (NNPF) for the current video unit, and the current video unit is a portion of a picture of the video.

Clause 234. A method for storing a bitstream of a video, comprising: performing a conversion between a current video unit of the video and the bitstream, wherein the bitstream comprises at least one set of syntax elements for activating at least one neural-network post-filter (NNPF) for the current video unit, and the current video unit is a portion of a picture of the video; and storing the bitstream in a non-transitory computer-readable recording medium.

Example Device

Fig. 11 illustrates a block diagram of a computing device 1100 in which various embodiments of the present disclosure can be implemented. The computing device 1100 may be implemented as or included in the source device 110 (or the video encoder 114 or 200) or the destination device 120 (or the video decoder 124 or 300) .

It would be appreciated that the computing device 1100 shown in Fig. 11 is merely for purpose of illustration, without suggesting any limitation to the functions and scopes of the embodiments of the present disclosure in any manner.

As shown in Fig. 11, the computing device 1100 includes a general-purpose computing device 1100. The computing device 1100 may at least comprise one or more processors or processing units 1110, a memory 1120, a storage unit 1130, one or more communication units 1140, one or more input devices 1150, and one or more output devices 1160.

In some embodiments, the computing device 1100 may be implemented as any user terminal or server terminal having the computing capability. The server terminal may be a server, a large-scale computing device or the like that is provided by a service provider. The user terminal may for example be any type of mobile terminal, fixed terminal, or portable terminal, including a mobile phone, station, unit, device, multimedia computer, multimedia tablet, Internet node, communicator, desktop computer, laptop computer, notebook computer, netbook computer, tablet computer, personal communication system (PCS) device, personal navigation device, personal digital assistant (PDA) , audio/video player, digital camera/video camera, positioning device, television receiver, radio broadcast receiver, E-book device, gaming device, or any combination thereof, including the accessories and peripherals of these devices, or any combination thereof. It would be contemplated that the computing device 1100 can support any type of interface to a user (such as “wearable” circuitry and the like) .

The processing unit 1110 may be a physical or virtual processor and can implement various processes based on programs stored in the memory 1120. In a multi-processor system, multiple processing units execute computer executable instructions in parallel so as to improve the parallel processing capability of the computing device 1100. The processing unit 1110 may also be referred to as a central processing unit (CPU) , a microprocessor, a controller or a microcontroller.

The computing device 1100 typically includes various computer storage medium. Such medium can be any medium accessible by the computing device 1100, including, but not limited to, volatile and non-volatile medium, or detachable and non-detachable medium. The memory 1120 can be a volatile memory (for example, a register, cache, Random Access Memory (RAM) ) , a non-volatile memory (such as a Read-Only Memory (ROM) , Electrically Erasable Programmable Read-Only Memory (EEPROM) , or a flash memory) , or any combination thereof. The storage unit 1130 may be any detachable or non-detachable medium and may include a machine-readable medium such as a memory, flash memory drive, magnetic disk or another other media, which can be used for storing information and/or data and can be accessed in the computing device 1100.

The computing device 1100 may further include additional detachable/non-detachable, volatile/non-volatile memory medium. Although not shown in Fig. 11, it is possible to provide a magnetic disk drive for reading from and/or writing into a detachable and non-volatile magnetic disk and an optical disk drive for reading from and/or writing into a detachable non-volatile optical disk. In such cases, each drive may be connected to a bus (not shown) via one or more data medium interfaces.

The communication unit 1140 communicates with a further computing device via the communication medium. In addition, the functions of the components in the computing device 1100 can be implemented by a single computing cluster or multiple computing machines that can communicate via communication connections. Therefore, the computing device 1100 can operate in a networked environment using a logical connection with one or more other servers, networked personal computers (PCs) or further general network nodes.

The input device 1150 may be one or more of a variety of input devices, such as a mouse, keyboard, tracking ball, voice-input device, and the like. The output device 1160 may be one or more of a variety of output devices, such as a display, loudspeaker, printer, and the like. By means of the communication unit 1140, the computing device 1100 can further communicate with one or more external devices (not shown) such as the storage devices and display device, with one or more devices enabling the user to interact with the computing device 1100, or any devices (such as a network card, a modem and the like) enabling the computing device 1100 to communicate with one or more other computing devices, if required. Such communication can be performed via input/output (I/O) interfaces (not shown) .

In some embodiments, instead of being integrated in a single device, some or all components of the computing device 1100 may also be arranged in cloud computing architecture. In the cloud computing architecture, the components may be provided remotely and work together to implement the functionalities described in the present disclosure. In some embodiments, cloud computing provides computing, software, data access and storage service, which will not require end users to be aware of the physical locations or configurations of the systems or hardware providing these services. In various embodiments, the cloud computing provides the services via a wide area network (such as Internet) using suitable protocols. For example, a cloud computing provider provides applications over the wide area network, which can be accessed through a web browser or any other computing components. The software or components of the cloud computing architecture and corresponding data may be stored on a server at a remote position. The computing resources in the cloud computing environment may be merged or distributed at locations in a remote data center. Cloud computing infrastructures may provide the services through a shared data center, though they behave as a single access point for the users. Therefore, the cloud computing architectures may be used to provide the components and functionalities described herein from a service provider at a remote location. Alternatively, they may be provided from a conventional server or installed directly or otherwise on a client device.

The computing device 1100 may be used to implement video encoding/decoding in embodiments of the present disclosure. The memory 1120 may include one or more video coding modules 1125 having one or more program instructions. These modules are accessible and executable by the processing unit 1110 to perform the functionalities of the various embodiments described herein.

In the example embodiments of performing video encoding, the input device 1150 may receive video data as an input 1170 to be encoded. The video data may be processed, for example, by the video coding module 1125, to generate an encoded bitstream. The encoded bitstream may be provided via the output device 1160 as an output 1180.

In the example embodiments of performing video decoding, the input device 1150 may receive an encoded bitstream as the input 1170. The encoded bitstream may be processed, for example, by the video coding module 1125, to generate decoded video data. The decoded video data may be provided via the output device 1160 as the output 1180.

While this disclosure has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present application as defined by the appended claims. Such variations are intended to be covered by the scope of this present application. As such, the foregoing description of embodiments of the present application is not intended to be limiting.

Claims

A method for video processing, comprising:

performing a conversion between a current video unit of a video and a bitstream of the video, wherein the bitstream comprises at least one set of syntax elements for activating at least one neural-network post-filter (NNPF) for the current video unit, and the current video unit is a portion of a picture of the video.
The method of claim 1, wherein the at least one set of syntax elements is comprised in a video message unit in the bitstream.
The method of claim 2, wherein the video message unit is a supplemental enhancement information (SEI) message.
The method of claim 2, wherein the video message unit is a neural-network post-filter activation (NNPFA) SEI message.
The method of any of claims 1-4, wherein each set of syntax elements in the at least one set of syntax elements is represented by SE_activation.
The method of any of claims 1-5, wherein a first set of syntax elements in the at least one set of syntax elements comprises a plurality of syntax elements.
The method of claim 6, wherein the first set of syntax element comprises a first syntax element indicating an NNPF specified by one or more neural-network post-filter characteristics (NNPFC) SEI messages that pertain to the picture.
The method of claim 7, wherein the first syntax element is represented by nnpfa_id.
The method of any of claims 6-8, wherein the first set of syntax element comprises a syntax element indicating the number of the at least one NNPF.
The method of any of claims 6-9, wherein the first set of syntax element comprises a syntax element indicating a color component range.
The method of any of claims 6-10, wherein the first set of syntax element comprises a syntax element indicating a purpose of the color component range.
The method of any of claims 1-11, wherein the current video unit comprises one of the following:

a part of a video,

a sub-region within the video,

a part of a sequence,

a sub-region within the sequence,

a sub-region within the picture,

a slice,

a part of the slice,

a sub-region within the slice,

a tile,

a part of the tile,

a sub-region within the tile,

a brick,

a part of the brick,

a sub-region within the brick,

a subpicture,

one or more coding tree units (CTUs) ,

one or more coding tree blocks (CTBs) ,

a CTU row,

a CTB row,

one or more coding units (CUs) ,

one or more coding blocks (CBs) , or

one or more virtual pipeline data units (VPDUs) .
The method of any of claims 1-11, wherein the current video unit comprises a set of patches of the picture.
The method of claim 13, wherein one of the set of patches is a rectangular array of samples from at least one color component of the picture.
The method of claim 14, wherein the at least one color component comprises at least one of the following:

a luma component, or

a chroma component.
The method of claim 14, wherein the at least one color component comprises at least one of the following:

a Y component,

a U component, or

a V component.
The method of claim 14, wherein the at least one color component comprises at least one of the following:

a red (R) component, or

a green (G) component, or

a blue (B) component.
The method of claim 13, wherein information regarding a patch in the set of patches is indicated in a video message in the bitstream.
The method of claim 18, wherein the video message is an NNPFC SEI message.
The method of any of claims 18-19, wherein a width of the patch is equal to a horizontal sample count of a patch size required for an input to the at least one NNPF, or

the width of the patch is equal to a multiple of the horizontal sample count.
The method of claim 20, wherein the horizontal sample count is indicated by a syntax element nnpfc_patch_width_minus1.
The method of any of claims 18-21, wherein a height of the patch is equal to a vertical sample count of a patch size required for an input to the at least one NNPF, or

the height of the patch is equal to a multiple of the vertical sample count.
The method of claim 22, wherein the vertical sample count is indicated by a syntax element nnpfc_patch_height_minus1.
The method of any of claims 1-11, wherein the current video unit comprises a set of regions of the picture.
The method of claim 24, wherein one of the set of regions comprises one or more initial points.
The method of claim 25, wherein each of the one or more initial points comprise a horizontal coordinate and a vertical coordinate.
The method of any of claims 24-26, wherein one of the set of regions comprises one or more ending points.
The method of claim 27, wherein each of the one or more ending points comprise a horizontal coordinate and a vertical coordinate.
The method of any of claims 24-28, wherein size information of a region in the set of regions comprises at least one of the following:

a width of the region, or

a height of the region.
The method of claim 24, wherein a region in the set of regions is determined based on an output of segmenting a decoded output picture of the video.
The method of claim 30, wherein the region comprises one of the following:

all foreground regions of the decoded output picture,

all background regions of the decoded output picture, or

a type of content in the decoded output picture.
The method of claim 24, wherein a region in the set of regions is determined based on an output of applying object classification or object detection on a decoded output picture of the video.
The method of claim 32, wherein the region comprises one or more classes of detected objects.
The method of claim 32, wherein the region comprises a region of the decoded output picture that does not comprise any detected objects.
The method of any of claims 2-34, wherein whether the at least one set of syntax elements is applied to a further video unit of the video is dependent on a relative relationship regarding signaling the further video unit and the video message unit.
The method of claim 35, wherein the further video unit is signaled after the video message unit, and the at least one set of syntax elements is applied to the further video unit.
The method of claim 35, wherein the further video unit is signaled before the video message unit, and the at least one set of syntax elements is applied to the further video unit.
The method of any of claims 1-37, wherein the at least one set of syntax elements is dependent on at least one of color components or a color format of the current video unit.
The method of any of claims 1-38, wherein an NNPFA SEI message in the bitstream comprises at least one second syntax element indicating a purpose of a color component range.
The method of claim 39, wherein the at least one second syntax element is represented by SE_color_purpose.
The method of any of claims 39-40, wherein a first purpose of the color component range is that only a single set of syntax elements for activating the at least one NNPF is comprised in an NNPFA SEI message and the activation of the at least one NNPF controlled by the single set of syntax elements is commonly used for one or more color components available to the at least one NNPF.
The method of claim 41, wherein the one or more color components is indicated in an NNPFC SEI message or determined based on a design of the at least one NNPF.
The method of any of claims 41-42, wherein a value of one of the at least one second syntax element equal to a first value indicates the first purpose.
The method of claim 43, wherein the first value is 0.
The method of any of claims 39-44, wherein a second purpose of the color component range is that only a single set of syntax elements for activating the at least one NNPF is comprised in an NNPFA SEI message and the activation of the at least one NNPF controlled by the single set of syntax elements is commonly used for all color components in the color component range.
The method of claim 45, wherein a value of one of the at least one second syntax element equal to a second value indicates the second purpose.
The method of claim 46, wherein the second value is 1.
The method of any of claims 39-47, wherein a third purpose of the color component range is that a plurality of sets of syntax elements for activating the at least one NNPF are comprised in an NNPFA SEI message and used for different color components in the color component range.
The method of claim 48, wherein a value of one of the at least one second syntax element equal to a third value indicates the third purpose.
The method of claim 49, wherein the third value is 2.
The method of any of claims 1-38, wherein at least one second syntax element indicating a purpose of color component range is not comprised in the bitstream.
The method of claim 51, wherein the purpose of the color component range is predetermined.
The method of any of claims 39-52, wherein an NNPFA SEI message in the bitstream comprises at least one third syntax element indicating the color component range.
The method of claim 53, wherein the at least one third syntax element is represented by SE_color_range.
The method of any of claims 53-54, wherein the at least one set of syntax elements for activating the at least one NNPF is used for all color components in the color component range.
The method of any of claims 53-55, wherein whether to signal the at least one third syntax element is dependent on the at least one second syntax element.
The method of claim 56, wherein if a value of the at least one second syntax element is equal to a first predetermined value, the at least one third syntax element is signaled, and

if the value of the at least one second syntax element is equal to a second predetermined value, the at least one third syntax element is not signaled.
The method of claim 55, wherein the at least one set of syntax elements for activating the at least one NNPF comprises only a single set of syntax elements, and the single set of syntax elements is commonly used for all color components in the color component range.
The method of claim 55, wherein the at least one set of syntax elements for activating the at least one NNPF comprises a plurality of sets of syntax elements, and the plurality of sets of syntax elements are used for different color components in the color component range.
The method of claim 59, wherein the number of the plurality of sets of syntax elements is equal to the number of the different color components.
The method of any of claims 39-60, wherein the color component range comprises at least one of the following:

a Y component,

a U component, or

a V component.
The method of any of claims 39-60, wherein the color component range comprises at least one of the following:

an R component, or

a G component, or

a B component.
The method of any of claims 39-62, wherein the maximum number of color component in the color component range is 1, 2, or 3.
The method of any of claims 1-63, wherein the at least one set of syntax elements comprises one set of syntax elements applied for a plurality of color components.
The method of claim 64, wherein the plurality of color components comprise all color components.
The method of claim 64, wherein the plurality of color components comprise at least one of the following:

a Y component,

a chroma blue (Cb) component, or

a chroma red (Cr) component.
The method of claim 64, wherein the plurality of color components comprise at least one of the following:

an R component, or

a G component, or

a B component.
The method of claim 64, wherein the plurality of color components comprise chroma components.
The method of claim 64, wherein the plurality of color components comprise Cb and Cr components.
The method of any of claims 1-63, wherein the at least one set of syntax elements comprises a plurality of sets of syntax elements applied for a plurality of color components separately.
The method of claim 70, wherein the plurality of sets of syntax elements are applied for all color components separately.
The method of claim 71, wherein the plurality of sets of syntax elements comprise a first set of syntax elements applied for a first color component.
The method of claim 72, wherein the first color component is one of a Y component, a Cb component, a Cr component, an R component, a G component or a B component.
The method of any of claims 71-73, wherein the plurality of sets of syntax elements comprise a second set of syntax elements applied for a second color component.
The method of claim 74, wherein the second color component is one of a Y component, a Cb component, a Cr component, an R component, a G component or a B component.
The method of any of claims 71-75, wherein the plurality of sets of syntax elements comprise a third set of syntax elements applied for a third color component.
The method of claim 76, wherein the third color component is one of a Y component, a Cb component, a Cr component, an R component, a G component or a B component.
The method of claim 70, wherein the plurality of sets of syntax elements are applied for luma and chroma components separately.
The method of claim 78, wherein the plurality of sets of syntax elements comprises a fourth set of syntax elements applied for the luma component.
The method of claim 79, wherein the plurality of sets of syntax elements comprises a fifth set of syntax elements applied for the chroma component.
The method of claim 80, wherein the fifth set of syntax elements are the same for Cb and Cr components.
The method of any of claims 1-81, wherein information regarding whether to and/or how to signal the at least one set of syntax elements is dependent on the number of the at least one NNPF.
The method of claim 82, wherein an NNPFA SEI message in the bitstream comprises a fourth syntax element indicating the number of the at least one NNPF.
The method of claim 83, wherein the fourth syntax element is represented by nnpfa_num_minus1.
The method of any of claims 83-84, wherein the number of the at least one NNPF is equal to a sum of a value of the fourth syntax element and a predetermined value.
The method of any of claims 83-85, wherein a value of the fourth syntax element is in a predetermine range.
The method of claim 86, wherein the predetermined range is from 0 to 2^k-1, and k is an integer.
The method of any of claims 83-87, wherein the fourth syntax element is an unsigned integer 0-th order Exp-Golomb-coded syntax element with the left bit first.
The method of any of claims 1-88, wherein the number of the at least one NNPF is smaller than the maximum value of a syntax element nnpfc_id plus one.
The method of any of claims 1-82, wherein the number of the at least one NNPF is not indicated in the bitstream.
The method of claim 90, wherein the number of the at least one NNPF is preset.
The method of any of claims 90-91, wherein the number of the at least one NNPF is 1.
The method of any of claims 1-92, wherein an NNPFA SEI message in the bitstream comprises at least one fifth syntax element, and one of the at least one fifth syntax element indicates an identification of one of the at least one NNPF.
The method of claim 93, wherein one of the at least one fifth syntax element is represented by nnpfa_id.
The method of any of claims 93-94, wherein the at least one fifth syntax element is comprised in the at least one set of syntax elements.
The method of any of claims 93-95, wherein the at least one fifth syntax element comprises a plurality of fifth syntax elements.
The method of any of claims 93-96, wherein the number of the at least one fifth syntax element is dependent on a color component of the current video unit.
The method of any of claims 93-97, wherein the number of the at least one fifth syntax element is dependent on the number of the at least one NNPF.
The method of any of claims 1-98, wherein the bitstream further comprises at least one sixth syntax element indicating a video unit type of the at least one NNPF.
The method of claim 99, wherein the at least one sixth syntax element is comprised in at least one of the following:

an NNPFA SEI message, or

an NNPFC SEI message.
The method of any of claims 99-100, wherein the at least one sixth syntax element is comprised in the at least one set of syntax elements.
The method of any of claims 99-101, wherein the at least one sixth syntax element is represented by SE_region_type or nnpfa_region_type.
The method of any of claims 99-102, wherein an NNPFA SEI message in the bitstream comprises at least one seventh syntax element indicating a video unit scope of the at least one NNPF for a corresponding video unit type.
The method of claim 103, wherein the at least one seventh syntax element is represented by SE_region_scope.
The method of any of claims 103-104, wherein the at least one seventh syntax element is comprised in the at least one set of syntax elements.
The method of any of claims 103-104, wherein the video unit type is a region, and the at least one seventh syntax element is comprised in the at least one set of syntax elements.
The method of any of claims 103-106, wherein the video unit scope is dependent on the video unit type.
The method of any of claims 103-107, wherein if the video unit type is a predetermined type, the video unit type is not indicated in the bitstream.
The method of any of claims 103-107, wherein if the video unit type is a predetermined type, the video unit type is indicated in the bitstream.
The method of any of claims 108-109, wherein the predetermined type is a picture.
The method of any of claims 99-110, wherein the video unit type is one of the following:

a sequence,

a picture,

a slice,

a tile,

a brick

a subpicture,

a subregion within the picture,

a subregion within the slice,

a subregion within the tile, or

a subregion within the brick.
The method of any of claims 99-110, wherein the video unit type is a CTU.
The method of claim 112, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating an identification of CTUs to which the at least one NNPF is applied.
The method of claim 113, wherein the identification of CTUs comprises coordinates of CTUs, or a sequence of indexes of CTUs.
The method of any of claims 99-110, wherein the video unit type is a CTB.
The method of claim 115, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating an identification of CTBs to which the at least one NNPF is applied.
The method of claim 116, wherein the identification of CTBs comprises coordinates of CTBs, or a sequence of indexes of CTBs.
The method of any of claims 99-110, wherein the video unit type is a CTU row.
The method of claim 118, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating an identification of a CTU row to which the at least one NNPF is applied.
The method of claim 119, wherein the identification of the CTU row comprises coordinates of the CTU row, or a sequence of indexes of the CTU row.
The method of any of claims 99-110, wherein the video unit type is a CTB row.
The method of claim 121, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating an identification of a CTB row to which the at least one NNPF is applied.
The method of claim 122, wherein the identification of the CTB row comprises coordinates of the CTB row, or a sequence of indexes of the CTB row.
The method of any of claims 99-110, wherein the video unit type is a CU.
The method of claim 124, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating an identification of CUs to which the at least one NNPF is applied.
The method of claim 125, wherein the identification of CUs comprises coordinates of CUs, or a sequence of indexes of CUs.
The method of any of claims 99-110, wherein the video unit type is a CB.
The method of claim 127, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating an identification of CBs to which the at least one NNPF is applied.
The method of claim 128, wherein the identification of CBs comprises coordinates of CBs, or a sequence of indexes of CBs.
The method of any of claims 99-110, wherein the video unit type is a VPDU.
The method of claim 131, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating an identification of VPDUs to which the at least one NNPF is applied.
The method of claim 131, wherein the identification of VPDUs comprises coordinates of VPDUs, or a sequence of indexes of VPDUs.
The method of any of claims 99-110, wherein the video unit type is a patch.
The method of claim 133, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating a size of a patch to which the at least one NNPF is applied.
The method of any of claims 133-134, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating at least one of the following:

the horizontal number of patches to which the at least one NNPF is applied,

the vertical number of the patches, or

the total number of the patches.
The method of any of claims 99-110, wherein the video unit type is a region.
The method of claim 136, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating at least one of the following:

an initial point of a region to which the at least one NNPF is applied,

an ending point of the region,

a width of the region, or

a height of the region.
The method of any of claims 1-98, wherein a video unit type of the at least one NNPF is not indicated in the bitstream.
The method of claim 138, wherein the video unit type is preset.
The method of any of claims 138-139, wherein the video unit type is a picture.
The method of any of claims 138-139, wherein the video unit type has the lowest level.
The method of claim 141, wherein the lowest level is a patch level.
The method of any of claims 138-142, wherein the at least one set of syntax elements are signaled in an order.
The method of claim 143, wherein a syntax element at a sequence level is signaled after a syntax element at a picture level.
The method of any of claims 1-144, wherein an NNPFA SEI message in the bitstream comprises at least one eighth syntax element indicating an activation of the at least one NNPF.
The method of claim 145, wherein the at least one eighth syntax element is dependent on a video unit type.
The method of claim 146, wherein only syntax elements at a level of a target video unit type are comprised in the NNPFA SEI message.
The method of claim 147, wherein if the target video unit type is a picture, the NNPFA SEI message comprises a syntax element indicating the activation of the at least one NNPF at a picture level, or

if the target video unit type is a slice, the NNPFA SEI message comprises a syntax element indicating the activation of the at least one NNPF at a slice level, or

if the target video unit type is a CTU, the NNPFA SEI message comprises a syntax element indicating the activation of the at least one NNPF at a CTU level.
The method of any of claims 1-144, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating the activation of the at least one NNPF at a video unit level.
The method of claim 149, wherein syntax elements for different video unit levels are signaled in an order.
The method of claim 150, wherein a syntax element for a first video unit level is signaled before a syntax element for a second video unit level, and the first video unit level is higher than the second video unit level.
The method of any of claims 149-151, wherein the one or more syntax elements comprises a ninth syntax element indicating whether the at least one NNPF is used at a current video unit level of the current video unit.
The method of claim 152, wherein the ninth syntax element equal to a fourth value indicates that the at least one NNPF is not used at the current video unit level, or

the ninth syntax element equal to a fifth value indicates that the at least one NNPF is used at the current video unit level, or

the ninth syntax element greater than the fourth value indicates that the at least one NNPF is used at the current video unit level.
The method of claim 153, wherein the fourth value is 0 or the fifth value is 1.
The method of any of claims 149-154, wherein the one or more syntax elements comprises a tenth syntax element indicating one of the following:

how to select an NNPF used at a current video unit level of the current video unit, or

the NNPF used at the current video level.
The method of claim 155, wherein the tenth syntax element greater than a sixth value indicates that an NNPF with an index equal to a value of the tenth syntax element minus one is used at the current video unit level.
The method of claim 156, wherein the sixth value is 0.
The method of claim 155, wherein the tenth syntax element smaller than the maximum number of NNPFs indicates that an NNPF with an index equal to a value of the tenth syntax element is used at the current video unit level.
The method of any of claims 149-158, wherein the one or more syntax elements comprises an eleventh syntax element indicating whether an NNPF is adaptively selected at a third video unit level lower than a current video unit level of the current video unit.
The method of claim 159, wherein the eleventh syntax element equal to a seventh value indicates that the NNPF is adaptively selected at the third video unit level, or

the eleventh syntax element equal to the maximum number of NNPFs indicates that the NNPF is adaptively selected at the third video unit level, or

the eleventh syntax element equal to the maximum number of NNPFs minus one indicates that the NNPF is adaptively selected at the third video unit level.
The method of claim 160, wherein the seventh value is 0.
The method of any of claims 149-161, wherein signaling of syntax element at a current video unit level of the current video unit is dependent on a syntax element at a video unit level higher than the current video unit level.
The method of any of claims 149-162, wherein an area of a first video unit being larger than an area of a second video unit indicates that a video unit level of the first video unit is greater than a video unit level of the second video unit.
The method of any of claims 149-163, wherein a picture level is lower than a sequence level, a slice level is lower than the picture level, a CTU level is lower than the slice level, and a CU level is lower than the CTU level.
The method of any of claims 1-164, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating the activation of the at least one NNPF at a sequence level.
The method of any of claims 1-164, wherein an NNPFA SEI message in the bitstream comprises a syntax element indicating the activation of the at least one NNPF at a sequence level or a level lower than the sequence level.
The method of any of claims 1-164, wherein a syntax element indicating the activation of the at least one NNPF at a sequence level is not indicated in the bitstream.
The method of any of claims 1-167, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating the activation of the at least one NNPF at a temporal layer ID (TID) level.
The method of claim 168, wherein the one or more syntax elements are dependent on a syntax element at a level higher than the TID level.
The method of any of claims 1-167, wherein an NNPFA SEI message in the bitstream comprises a syntax element indicating the activation of the at least one NNPF at a TID level or a level lower than the TID level.
The method of claim 170, wherein the NNPFA SEI message further comprises a syntax element indicating an TID index.
The method of any of claims 1-167, wherein a syntax element indicating the activation of the at least one NNPF at a TID level is not indicated in the bitstream.
The method of any of claims 1-172, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating the activation of the at least one NNPF at a picture level.
The method of claim 173, wherein the one or more syntax elements are dependent on a syntax element at a level higher than the picture level.
The method of any of claims 1-172, wherein an NNPFA SEI message in the bitstream comprises a syntax element indicating the activation of the at least one NNPF at a picture level or a level lower than the picture level.
The method of any of claims 1-172, wherein an NNPFA SEI message in the bitstream comprises a syntax element indicating whether the at least one NNPF is activated at a picture level.
The method of any of claims 173-176, wherein the NNPFA SEI message further comprises a syntax element indicating an index of a NNPF applied at the picture level.
The method of any of claims 1-172, wherein a syntax element indicating the activation of the at least one NNPF at a picture level is not indicated in the bitstream.
The method of any of claims 1-178, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating the activation of the at least one NNPF at a slice level.
The method of claim 179, wherein the one or more syntax elements are dependent on a syntax element at a level higher than the slice level.
The method of any of claims 1-178, wherein an NNPFA SEI message in the bitstream comprises a syntax element indicating the activation of the at least one NNPF at a slice level or a level lower than the slice level.
The method of any of claims 1-178, wherein a syntax element indicating the activation of the at least one NNPF at a slice level is not indicated in the bitstream.
The method of any of claims 1-182, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating the activation of the at least one NNPF at a target video unit level.
The method of claim 183, wherein the one or more syntax elements are dependent on a syntax element at a level higher than the target video unit level.
The method of any of claims 1-182, wherein an NNPFA SEI message in the bitstream comprises a syntax element indicating the activation of the at least one NNPF at a target video unit level or a level lower than the target video unit level.
The method of any of claims 1-182, wherein an NNPFA SEI message in the bitstream comprises a syntax element indicating whether the at least one NNPF is activated at a target video unit level.
The method of any of claims 183-186, wherein the NNPFA SEI message further comprises a syntax element indicating an index of a NNPF applied at the target video unit level.
The method of any of claims 1-182, wherein a syntax element indicating the activation of the at least one NNPF at a target video unit level is not indicated in the bitstream.
The method of any of claims 182-188, wherein the target video unit level is one of the following:

a sub-block level,

a CTU level,

a CTB level, or

a patch level.
The method of any of claims 1-189, wherein an NNPFA SEI message in the bitstream comprises one or more syntax elements indicating the activation of the at least one NNPF at a region level.
The method of claim 190, wherein the one or more syntax elements are dependent on a syntax element at a level higher than the region level.
The method of any of claims 1-189, wherein an NNPFA SEI message in the bitstream comprises a syntax element indicating the activation of the at least one NNPF at a region level or a level lower than the region level.
The method of any of claims 1-189, wherein a syntax element indicating the activation of the at least one NNPF at a region level is not indicated in the bitstream.
The method of any of claims 145-193, wherein syntax elements in the NNPFA SEI message are used for the same video unit or region until a further sequence or a further SEI message is processed.
The method of any of claims 145-193, wherein syntax elements in the NNPFA SEI message are used for the nearest video unit or region.
The method of any of claims 1-195, wherein one or more syntax element indicating a quality improvement of the current video unit associated with one of the at least one NNPF is comprised in at least one of an NNPFA SEI message or an NNPFC SEI message.
The method of any of claims 1-196, wherein one or more syntax element indicating a purpose of one of the at least one NNPF is comprised in at least one of an NNPFA SEI message or an NNPFC SEI message.
The method of claim 197, wherein the purpose comprises improving a subjective quality of the current video unit or improving an objective quality of the current video unit.
The method of claim 1-198, wherein one or more syntax element indicating a performance level of one of the at least one NNPF is comprised in at least one of an NNPFA SEI message or an NNPFC SEI message.
The method of claim 199, wherein the performance level is a normalized value.
The method of claim 199, wherein the performance level is different for different purposes of the NNPC, or the performance level is the same for different purposes of the NNPC.
The method of claim 1-201, wherein one or more syntax element indicating a complexity level of one of the at least one NNPF is comprised in at least one of an NNPFA SEI message or an NNPFC SEI message.
The method of claim 202, wherein the complexity level is a normalized value.
The method of any of claims 1-203, wherein an NNPFC SEI message in the bitstream comprises one or more sets of syntax elements indicating at least one of a plurality of NNPFs or characteristics of NNPF.
The method of claim 204, wherein the NNPFC SEI message comprises a twelfth syntax element indicating the number of the plurality of NNPFs.
The method of claim 205, wherein the twelfth syntax element is represented by nnpfc_num_minus1.
The method of any of claims 205-206, wherein the number of the plurality of NNPFs is equal to a sum of a value of the twelfth syntax element and a predetermined value.
The method of any of claims 205-207, wherein a value of the twelfth syntax element is in a predetermine range.
The method of claim 208, wherein the predetermined range is from 0 to 2^k-1, and k is an integer.
The method of any of claims 205-209, wherein the twelfth syntax element is an unsigned integer 0-th order Exp-Golomb-coded syntax element with the left bit first.
The method of any of claims 1-210, wherein the number of the plurality of NNPFs is smaller than the maximum value of a syntax element nnpfc_id plus one.
The method of claim 204, wherein the number of the plurality of NNPFs is not indicated in the bitstream.
The method of claim 212, wherein the number of the plurality of NNPFs is preset.
The method of any of claims 212-213, wherein the number of the plurality of NNPFs is one of 1, 2, 3, 4, or 5.
The method of any of claims 204-214, wherein the number of the one or more sets of syntax elements is dependent on the number of the plurality of NNPFs.
The method of claim 215, wherein the number of the one or more sets of syntax elements is equal to the number of the plurality of NNPFs.
The method of any of claims 1-203, wherein the at least one NNPF comprises a plurality of NNPFs, and a plurality of sets of syntax elements indicating characteristics of NNPF are signaled for different NNPFs in the plurality of NNPFs.
The method of claim 217, wherein each of the at least one NNPF is associated with a set of syntax elements indicating characteristics of NNPF.
The method of claim 217, wherein the plurality of sets of syntax elements are signaled in an order.
The method of claim 217, wherein the plurality of sets of syntax elements are signaled one by one.
The method of any of claims 217-220, wherein an i-th set of syntax element in the plurality of sets of syntax elements is used for an i-th NNPFs of the plurality of NNPFs, where i is an integer.
The method of claim 221, wherein i is 1, 2, or 3.
The method of any of claims 217-222, wherein a design of each set of syntax elements in the plurality of sets of syntax elements is the same.
The method of any of claims 217-222, wherein at least one of the following is the same:

the number of syntax elements in each set of syntax elements among the plurality of sets of syntax elements, or

syntax elements in each set of syntax elements among the plurality of sets of syntax elements.
The method of any of claims 217-222, wherein each set of syntax elements in the plurality of sets of syntax elements comprises a thirteenth syntax element indicating an identifying number of an NNPF.
The method of claim 225, wherein the thirteenth syntax element is represented by nnpfc_id.
The method of any of claims 225-226, wherein each set of syntax elements in the plurality of sets of syntax elements comprises a fourteenth syntax element indicating how to obtain an NNPF associated with a value of the thirteenth syntax element.
The method of claim 227, wherein the fourteenth syntax element is represented by nnpfc_mode_idc.
The method of any of claims 1-228, wherein the conversion includes encoding the current video unit into the bitstream.
The method of any of claims 1-228, wherein the conversion includes decoding the current video unit from the bitstream.
An apparatus for video processing comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to perform a method in accordance with any of claims 1-230.
A non-transitory computer-readable storage medium storing instructions that cause a processor to perform a method in accordance with any of claims 1-230.
A non-transitory computer-readable recording medium storing a bitstream of a video which is generated by a method performed by an apparatus for video processing, wherein the method comprises:

performing a conversion between a current video unit of the video and the bitstream, wherein the bitstream comprises at least one set of syntax elements for activating at least one neural-network post-filter (NNPF) for the current video unit, and the current video unit is a portion of a picture of the video.
A method for storing a bitstream of a video, comprising:

performing a conversion between a current video unit of the video and the bitstream, wherein the bitstream comprises at least one set of syntax elements for activating at least one neural-network post-filter (NNPF) for the current video unit, and the current video unit is a portion of a picture of the video; and

storing the bitstream in a non-transitory computer-readable recording medium.