Post-processing filtering process based on post-processing filter bank

Abstract

A mechanism for processing video data is disclosed. The mechanism includes determining to apply a processing chain of post-processing filters (PPFs) to the visual media data by obtaining a list of cropped decoded pictures arranged in an output order, selecting a processing chain, applying each PPF in the processing chain to each cropped decoded picture in the list, and applying each PPF in the processing chain to each of the cropped decoded pictures in the list. And replacing the cut decoded picture in the list with the processed picture. A conversion between the visual media data and the bitstream is performed based on the processing chain.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority and benefit to U.S. Provisional Patent Application No. 63 / 588,273, filed October 5, 2023, and U.S. Provisional Patent Application No. 63 / 574,088, filed April 3, 2024. All of the foregoing patent applications are incorporated herein by reference in their entirety. Technical Field

[0003] This patent document relates to the generation, storage, and use of digital audio and video media information in file formats. Background Technology

[0004] Digital video consumes the largest amount of bandwidth used on the internet and other digital communication networks. As the number of connected user devices capable of receiving and displaying video increases, the bandwidth demand for digital video is likely to continue to grow. Summary of the Invention

[0005] The first aspect relates to a method for processing video data, comprising: determining a processing chain of post-processing filters (PPFs) to be applied to visual media data by: obtaining a list of cropped decoded images arranged in output order; selecting a processing chain; applying each PPF in the processing chain to each cropped decoded image in the list; and replacing the cropped decoded images in the list with the processed images; and performing a conversion between the visual media data and a bitstream based on the processing chain.

[0006] The second aspect relates to a non-transitory computer-readable recording medium storing a bitstream of video generated by a method performed by a video processing apparatus, wherein the method includes: determining a processing chain for applying post-processing filters (PPFs) to visual media data by: obtaining a list of cropped decoded images arranged in output order; selecting a processing chain; applying each PPF in the processing chain to each cropped decoded image in the list; and replacing the cropped decoded images in the list with the processed images; and generating a bitstream based on the determination.

[0007] The third aspect relates to a method for storing a bitstream of video, comprising: determining a processing chain of post-processing filters (PPFs) to be applied to visual media data by: obtaining a list of cropped decoded images arranged in output order; selecting a processing chain; applying each PPF in the processing chain to each cropped decoded image in the list; and replacing the cropped decoded images in the list with the processed images; generating a bitstream based on the determination; and storing the bitstream in a non-transitory computer-readable recording medium.

[0008] The fourth aspect relates to an apparatus for processing video data, comprising: a processor; and a non-transitory memory having instructions thereon, wherein the instructions, when executed by the processor, cause the processor to perform any of the aforementioned aspects.

[0009] The fifth aspect relates to a non-transitory computer-readable medium including a computer program product for use by a video codec apparatus, the computer program product including computer-executable instructions stored on the non-transitory computer-readable medium, such that when the instructions are executed by a processor, the video codec apparatus performs the methods of any of the preceding aspects.

[0010] For clarity, any of the embodiments described above may be combined with one or more other embodiments described above to create new embodiments within the scope of this disclosure.

[0011] These and other features will become clearer through the following detailed description of the embodiments with reference to the accompanying drawings and claims. Attached Figure Description

[0012] To gain a more complete understanding of this disclosure, reference is now made to the following brief description, along with the accompanying drawings and detailed description, wherein similar reference numerals denote similar parts.

[0013] Figure 1 This is a block diagram illustrating an example video processing system.

[0014] Figure 2 This is a block diagram of an example video processing device.

[0015] Figure 3 This is a flowchart of an example method for video processing.

[0016] Figure 4 This is a block diagram illustrating an example video codec system.

[0017] Figure 5 This is a block diagram showing an example encoder.

[0018] Figure 6 This is a block diagram showing an example decoder.

[0019] Figure 7 This is a schematic diagram of an example encoder.

[0020] Figure 8 This is a flowchart of an example method for video processing. Detailed Implementation

[0021] First, it should be understood that although illustrative implementations of one or more embodiments are provided below, the disclosed systems and / or methods can be implemented using any number of techniques, whether currently known or yet to be developed. This disclosure should not be limited in any way to the illustrative implementations, drawings, and techniques described below, including the exemplary designs and implementations shown and described herein, but rather to modifications within the scope of the appended claims and their full equivalents.

[0022] Chapter headings are used in this document for ease of understanding and not to limit the applicability of the techniques and embodiments disclosed in each chapter to that chapter only. Furthermore, H.266 terminology is used in some descriptions merely for ease of understanding and not to limit the scope of the disclosed techniques. Therefore, the techniques described herein are also applicable to other video codec protocols and designs. In this document, editorial changes relative to the Multi-Functional Video Codec (VVC) specification and / or the SEI Message (VSEI) standard for encoding and decoding video bitstreams are indicated in the text by bold italics (indicating deleted text) and bold text (indicating added text).

[0023] 1. Preliminary Discussion

[0024] This document relates to image / video codec techniques. Specifically, this disclosure relates to filtering processes based on post-processing filter banks. These ideas can be applied individually or in various combinations to video bitstreams encoded or decoded by any codec, such as the VVC standard and / or the Versatile SEI Message (VSEI) standard for encoding and decoding video bitstreams.

[0025] 2. Abbreviation

[0026] Adaptive Parameter Set (APS), Access Unit (AU), Codec Layer Video Sequence (CLVS), Codec Layer Video Sequence Start (CLVSS), Cyclic Redundancy Check (CRC), Codec Video Sequence (CVS), Finite Impulse Response (FIR), Intra-Frame Random Access Point (IRAP), Network Abstraction Layer (NAL), Picture Parameter Set (PPS), Picture Unit (PU), Random Access Skip Before (RASL) Picture, Supplemental Enhancement Information (SEI), Stepped Temporal Sublayer Access (STSA), Video Codec Layer (VCL), Multifunctional Supplemental Enhancement Information (VSEI) described in Recommendation ITU-T H.274 | ISO / IEC 23002-7, Video Availability Information (VUI), and Multifunctional Video Coding (VVC) described in Recommendation ITU-T H.266 | ISO / IEC 23090-3.

[0027] 3. Further discussion

[0028] 3.1 Video Coding and Decoding Standards

[0029] Video coding standards have evolved primarily through the development of standards by the International Telecommunication Union (ITU) Telecommunication Standardization Department (ITU-T) and the International Organization for Standardization (ISO) / International Electrotechnical Commission (IEC). ITU-T produced the H.261 and H.263 standards, ISO / IEC produced the Moving Picture Experts Group (MPEG)-1 and MPEG-4 Vision, and the two organizations jointly produced the H.262 / MPEG-2 video standard and the H.264 / MPEG-4 Advanced Video Coding (AVC) standard and the H.265 / High Efficiency Video Coding (HEVC) standard [1]. Starting with H.262, video coding standards are based on a hybrid video coding structure, which utilizes temporal prediction plus transform coding.

[0030] The Multi-Functional Video Coding (VVC) standard (ITU-T H.266 | ISO / IEC 23090-3) [2] and the related Multi-Functional Supplemental Enhancement Information (VSEI) standard (ITU-T H.274 | ISO / IEC 23002-7) [3] are designed for use in the widest range of applications, including simple uses such as television broadcasting, video conferencing or playback from storage media, as well as more advanced use cases such as adaptive bitrate streaming, video region extraction, synthesis and merging of content from multiple codec video bitstreams, multi-view video, scalable layer codecs and viewport adaptive 360° immersive media.

[0031] 3.2 General SEI Messages and SEI Messages in VVC

[0032] SEI messages assist in processes related to decoding, display, or other purposes. However, SEI messages are not essential for constructing luma or chroma samples during the decoding process. Standard-compliant decoders do not need to process this information to achieve output order consistency. Some SEI messages are necessary for checking bitstream consistency and output timing decoder consistency. Other SEI messages are not necessary for checking bitstream consistency.

[0033] Appendix D of VVC specifies the syntax and semantics of SEI message payloads for some SEI messages, and specifies the use of SEI messages and VUI parameters whose syntax and semantics are specified in ITU-TH.SEI | ISO / IEC 23002-7.

[0034] 3.3 SEI Processing Order (SPO) SEI Messages

[0035] JVET-AE2027 [4] includes a specification for an SEI message called SEI Processing Order (SPO) SEI message, which carries information indicating the preferred processing order of different types of SEI messages determined by the encoder (content producer) for codec video sequences (CVS) that may exist in the bitstream.

[0036] The SPO SEI message specification in JVET-AE2027 is as follows.

[0037] 3.3.1 General SEI Load Syntax

[0038]

[0039] 3.3.2 SEI Processing Order and SEI Message Syntax

[0040]

[0041] 3.3.3 SEI Processing Order and SEI Message Semantics

[0042] SEI Processing Order: SEI messages carry information indicating the preferred processing order for different types of SEI messages that may exist in CVS, as determined by the encoder (i.e., the content producer).

[0043] When an SEI processing order SEI message exists in any access unit of a CVS, it must also exist in the first access unit of the CVS. SEI processing order SEI messages continue from the current access unit in decoding order until the end of the CVS. When multiple SEI processing order SEI messages exist in a CVS, they must have the same content.

[0044] The requirement for bitstream consistency is that within the SEI processing order SEI message, there must be at least two pairs of syntax elements po_sei_payload_type[i] and po_sei_processing_order[i], and there must be at least two unequal po_sei_processing_order[i] values.

[0045] SEI processing order: SEI messages can carry one or more SEI prefix indicators for a specific payloadType. Each SEI prefix indicator is a byte string that follows the SEI payload syntax according to the value of that payloadType, and contains the number of complete syntax elements starting from the first syntax element in the SEI payload, and may be followed by bits that do not represent any complete syntax elements of the SEI payload.

[0046] These SEI prefixes should provide sufficient information to determine the specific processing order of SEI messages that have the same payloadType value but different preferred processing orders.

[0047] po_num_sei_messages_minus2 plus 2 indicates the number of SEI messages, which have the processing order indicated in the SEI processing order message.

[0048] po_sei_importance_flag[i] indicates the importance of the SEI message at index i, as determined by the encoder.

[0049] If the decoding system cannot interpret or does not support any SEI message with a po_sei_importance_flag[i] equal to 1, then the entire SEI processing order SEI message should be ignored.

[0050] The `reserved_alignment_6bits` parameter is meaningless and must be equal to 0 in a bitstream conforming to this version of the specification. The decoder must allow this syntax element to have other values ​​and must ignore such values.

[0051] If po_sei_wrapping_flag[i] equals 0, then the SEI message must exist outside the SEI processing order SEI message with payloadType equal to po_sei_payload_type[i]. However, if po_sei_wrapping_flag[i] equals 0 and no SEI message with payloadType equal to po_sei_payload_type[i] exists, then the following applies:

[0052] - If po_sei_importance_flag[i] equals 1, the decoder should ignore the entire SEI processing order SEI message.

[0053] Otherwise, the decoder must ignore all data associated with the loop variable value of i.

[0054] Note - `po_sei_wrapping_flag[i]` equal to 1 allows SEI messages to be carried within SEI messages processed in the SEI processing order, preventing such SEI messages from being misinterpreted by decoders that do not process SEI messages in the SEI processing order. Therefore, `po_sei_wrapping_flag[i]` equal to 1 is intended to be used when `po_sei_wrapping_flag[i]` equal to 0 would cause such decoders to produce unexpected results.

[0055] A value of 1 for po_sei_prefix_flag[i] indicates that po_num_prefix_bytes[i] exists. A value of 0 for po_sei_prefix_flag[i] indicates that po_num_prefix_bytes[i] does not exist.

[0056] `po_sei_payload_type[i]` specifies the `payloadType` value for the `i`-th SEI message type, providing preferred processing order information in the SEI message for that `i`-th SEI message type. For any two distinct non-negative integer values ​​`m` and `n`, the values ​​of `po_sei_payload_type[m]` and `po_sei_payload_type[n]` should not be the same unless both `po_sei_prefix_flag[m]` and `po_sei_prefix_flag[n]` are equal to 1.

[0057] SeiProcessingOrderSeiList is set to consist of payloadType values ​​as specified in entry D.2.1, except for the values ​​137, 144, 147, 148, 179, 180, 200, 201, 208, and 213. When po_sei_payload_type[i] is not equal to any value in SeiProcessingOrderSeiList, the value of po_sei_prefix_flag[i] must be equal to 0.

[0058] po_num_prefix_bytes[i] (if present) specifies the number of bytes associated with the i-th SEI message, providing preferred processing order information in the SEI processing order message for that i-th SEI message. If it does not exist, the value of po_num_prefix_bytes[i] is presumed to be 0.

[0059] po_prefix_byte[i][j] (if it exists) specifies the value of the j-th byte of the i-th SEI message.

[0060] po_sei_processing_order[i] indicates the preferred processing order for the i-th SEI message type, and provides preferred processing order information in the SEI processing order SEI message for the i-th SEI message type. For any two distinct integer values ​​m and n greater than or equal to 0, po_sei_processing_order[m] less than po_sei_processing_order[n] indicates that any SEI message type with payloadType equal to po_sei_payload_type[m] and (if present) bytes po_prefix_byte[m][p] in the range of 0 to po_num_prefix_bytes[m] - 1 (inclusive) should be processed before any SEI message type with payloadType equal to po_sei_payload_type[n] and (if present) bytes po_prefix_byte[n][q] in the range of 0 to po_num_prefix_bytes[n] - 1 (inclusive) and po_sei_processing_order[m] equal to po_sei_processing_order[n] indicates that there is no preferred processing order among the SEI message types. When multiple SEI messages exist and the values ​​of po_sei_payload_type[i], po_num_prefix_bytes[i], and byte po_prefix_byte[i][j] (j ranges from 0 to po_num_prefix_bytes[i] - 1, inclusive) are the same, they must have the same po_sei_processing_order[i].

[0061] po_sei_processing_order[0] must be equal to 0, and for i greater than 0, po_sei_processing_order[i] must be equal to po_sei_processing_order[i-1] or po_sei_processing_order[i-1]+1.

[0062] The value of po_sei_processing_order[ po_num_sei_messages_minus2 + 1 ] should not be equal to 0.

[0063] 3.4 Signaling of Neural Network Post-processing Filters

[0064] JVET-AE2006 [5] includes provisions for two SEI messages (i.e., the Neural Network Post-Processing Filter Feature (NNPFC) SEI message and the Neural Network Post-Processing Filter Activation (NNPFA) SEI) for signaling used in neural network post-processing filters. JVET-AE2005 [6] includes provisions for the use of NNPFC SEI messages in VVC bitstreams.

[0065] The specifications for NNPFC SEI and NNPFA SEI messages in JVET-AE2006, and the specifications for the use of NNPFC SEI messages in VVC bitstreams in JVET-AE2005 are as follows.

[0066] 8.28 Neural Network Post-Processing Filter SEI Message

[0067] 8.28.1 General Post-Processing Filtering Procedure Using NNPF

[0068] 8.28.1.2 Overview

[0069] The input to this process is a bitstream, BitstreamToFilter. The output is a list of NNPF output images, ListNnpfOutputPics.

[0070] First, BitstreamToFilter is decoded, and the list CroppedDecodedPictures is set to a list of cropped decoded images generated from decoding BitstreamToFilter in output order.

[0071] Secondly, for each cropped decoded picture in CroppedDecodedPictures and for which one or more NNPFs are activated, the filtering process for a picture as specified in Entry 8.28.1.2 is called repeatedly in the order of output.

[0072] The order of the images in ListNnpfOutputPics is the output order.

[0073] Within ListNnpfOutputPics, there should not be more than one image associated with any particular output time instance. When multiple NNPFs are active for any particular image in CroppedDecodedPictures, and although any NNPF can be selected, only one of the multiple NNPFs is allowed to be applied, the above constraints apply regardless of which NNPF is selected for that particular image.

[0074] For any specific pair of images, inputPicA and inputPicB, consecutive in output order within CroppedDecodedPictures, if one or more images from ListNnpfOutputPics, interpolatedPicSetA, exist between inputPicA and inputPicB in output order, the images in interpolatedPicSetA must be one of the images output when the specific image currPicA in CroppedDecodedPictures is the current image by applying a specific NNPF nnpfA with PictureRateUpsamplingFlag equal to 1. No images should be output between inputPicA and inputPicB in output order if any other NNPF application (including nnpfA) is used in the filtering process for an image when currPicA is the current image, or if any other image currPicB in CroppedDecodedPictures is the current image in the filtering process for an image.

[0075] Note - The intent of the constraint expressed in the previous paragraph is to prohibit generating an NNPF output image more than once between any given consecutive input image pairs.

[0076] 9.28.1.2 Filtering process for an image using NNPF

[0077] The filtering procedure specified in this entry applies to each cropped decoded picture (referred to as the current picture) in CroppedDecodedPictures and for which one or more NNPFs are activated.

[0078] When NNPF is applied to the current image, the following applies:

[0079] - The filtered and / or interpolated image is generated by NNPF by applying the NNPF procedure specified in the semantics of the NNPFC SEI message to the current image in a block-by-block manner.

[0080] - The order in which images are generated by NNPF by applying the NNPF process, which is stored in the output tensor of NNPF, is the output order.

[0081] When the applied NNPF is the last NNPF applied to the current image, the images generated by the NNPF and output by the NNPF process are included in ListNnpfOutputPics, in the same order as when the images are stored in the output tensor of the NNPF.

[0082] 8.28.2 Characteristics of Neural Network Post-Processing Filters (SEI Messages)

[0083] 8.28.2.1 Characteristics of Neural Network Post-Processing Filters and SEI Message Syntax

[0084] …

[0085] 8.28.2.2 Characteristics of Neural Network Post-Processing Filters and Semantics of SEI Messages

[0086] The Neural Network Post-Processing Filter Characteristics (NNPFC) SEI message specifies the neural networks that can be used as post-processing filters. For a specific image, the specified use of a Neural Network Post-Processing Filter (NNPF) is indicated by the Neural Network Post-Processing Filter Activation (NNPFA) SEI message.

[0087] The following variables need to be specified when using this SEI message:

[0088] - Input image width and height in units of brightness samples, denoted as CroppedWidth and CroppedHeight in this paper, respectively.

[0089] - The luminance sample array CroppedYPic[idx] and chrominance sample arrays CroppedCbPic[idx] and CroppedCrPic[idx] (if present) of the input image, with index idx ranging from 0 to numInputPics - 1 (inclusive), are used as input to NNPF.

[0090] - BitDepth of the luminance sample array for the input image Y .

[0091] - BitDepth of the chroma sample array (if any) for the input image C .

[0092] - Chroma format indicator, referred to herein as ChromaFormatIdc, as described in sub-entry 7.3.

[0093] - When nnpfc_auxiliary_inp_idc equals 1, the filter strength control value array StrengthControlVal[idx] must contain real numbers in the range of 0 to 1 (inclusive) for the input image with index idx ranging from 0 to numInputPics - 1 (inclusive).

[0094] The input image at index 0 corresponds to the image activated by the NNPFA SEI message for its NNPF defined by the NNPFC SEI message. Input images with indices ranging from 1 to numInputPics - 1 (inclusive) precede the input images at index i - 1 in the output order.

[0095] …

[0096] D.12.11 Use of SEI messages for neural network post-processing filters and activation SEI messages for neural network post-processing filters

[0097] Let currPic be the cropped decoded output image. For this cropped decoded output image, activate the neural network post-processing filter (NNPF) defined by the neural network post-processing filter property (NNPFC) SEI message through the neural network post-processing filter activation (NNPFA) SEI message, and set currLayerId to the nuh_layer_id value of currPic.

[0098] The requirement for bitstream consistency is that when a picture unit contains an NNPFA SEI message, the value of ph_pic_output_flag in the picture header contained in that picture unit must be equal to 1.

[0099] Note - Since only the cropped decoded output image is used as the input image for NNPF, the value of ph_pic_output_flag in the image header of the encoded / decoded image corresponding to each input image of NNPF is equal to 1.

[0100] The variable pictureRateUpsamplingFlag is set to equal to ( ( nnpfc_purpose & 0x08 ) >0 ) ? 1 : 0.

[0101] The variable numInputPics is set to equal nnpfc_num_input_pics_minus1 + 1.

[0102] The variable numInferences is derived as follows:

[0103] - If all of the following conditions are true, then the variable numPostRoll is set to the value of i that makes nnpfc_interpolated_pics[i] greater than 0, and the variable numInferences is set to 1 + numPostRoll:

[0104] - nnpfc_purpose equals 8 (i.e., the sole purpose of NNPF is image rate upsampling).

[0105] - nnpfa_persistence_flag equals 1.

[0106] - Only for a single i value greater than 0, nnpfc_interpolated_pics[i] is greater than 0.

[0107] - Any of the following conditions is true:

[0108] - currPic is the last picture in the output order of the bitstream with nuh_layer_id equal to currLayerId.

[0109] - currPic is the last image in the CLVS in the output order, and nnpfa_no_foll_clvs_flag is equal to 1.

[0110] - Otherwise, if all of the following conditions are true, the variable numPostRoll is set to equal InpIdx[i], where the value of i makes nnpfa_output_flag[i] equal to 1, and the variable numInferences is set to equal 1 + numPostRoll:

[0111] - pictureRateUpsamplingFlag equals 0.

[0112] - numInputPics is greater than 1.

[0113] - nnpfa_persistence_flag equals 1.

[0114] - For a single idx value in the range of 0 to NumInpPicsInOutputTensor - 1 (inclusive), nnpfa_output_flag[idx] is equal to 1, and for that single idx value, InpIdx[idx] is greater than 0.

[0115] - Any of the following conditions is true:

[0116] - currPic is the last picture in the output order of the bitstream with nuh_layer_id equal to currLayerId.

[0117] - currPic is the last image in the CLVS in the output order, and nnpfa_no_foll_clvs_flag is equal to 1.

[0118] Otherwise, the variable numInferences is set to 1.

[0119] For each value of j in the range of 0 to numInferences - 1 (inclusive), the following applies:

[0120] - For i in the range of 0 to numInputPics - 1 (inclusive), the arrays inputPic[i] and inputPresentFlag[i] (which represent all input images and the existence of input images, respectively) are defined as follows:

[0121] - When j is greater than 0, for each k value in the range of 0 to j - 1 (inclusive), inputPic[k] is set to currPic, and inputPresentFlag[k] is set to 0.

[0122] - The j-th input image inputPic[j] is set to currPic, and inputPresentFlag[j] is set to 1.

[0123] - When numInputPics is greater than 1, for each value of i in the range from j + 1 to numInputPics - 1 (inclusive), sorted in ascending order of i, the following applies:

[0124] - If both of the following conditions are true, then inputPic[i] is set to prevPic, and inputPresentFlag[i] is set to 1:

[0125] - Any of the following conditions is true:

[0126] - pictureRateUpsamplingFlag equals 1, and currPic is associated with a frame packing arrangement SEI message having a specific value of frame_packing_arrangement_type equal to 5 and fp_current_frame_is_frame0_flag, and there exists a cropped decoded output image prevPic, which is the last image in output order among all cropped decoded output images. All cropped decoded output images have a nuh_layer_id equal to currLayerId, are in output order before inputPic[i-1], and are associated with a frame packing arrangement SEI message having the same value of frame_packing_arrangement_type equal to 5 and fp_current_frame_is_frame0_flag.

[0127] - if pictureRateUpsamplingFlag is equal to 0 or currPic is not associated with a frame packing arrangement SEI message with frame_packing_arrangement_type equal to 5, and there exists a cropped decoded output image prevPic, which is the last image in output order among all cropped decoded output images, and all cropped decoded output images have nuh_layer_id equal to currLayerId and are before inputPic[i - 1] in output order.

[0128] - nnpfa_no_prev_clvs_flag equals 0, or the encoding / decoding image corresponding to prevPic and the current image exist in the same CLVS.

[0129] - Otherwise, the following applies:

[0130] - inputPic[i] is set to the same image as inputPic[i-1], and inputPresentFlag[i] is set to 0.

[0131] - The requirement for bitstream consistency is that when pictureRateUpsamplingFlag is equal to 1, nnpfc_interpolated_pics[i-1] must be equal to 0.

[0132] - The requirement for bitstream consistency is that when inputPresentFlag[i] equals 0 and nnpfc_input_pic_output_flag[i] equals 1, for the value of idx that makes InpIdx[idx] equal to i, the value of nnpfa_output_flag[idx] must be equal to 0.

[0133] - To interpret NNPFC SEI messages, the following variables are specified:

[0134] - If numInputPics is greater than 1 and there exists a second NNPF defined by at least one NNPFC SEI message, activated by an NNPFA SEI message for currPic, and having an nnpfc_purpose equal to 4, then the following applies:

[0135] - CroppedWidth is set to be equal to nnpfcOutputPicWidth as defined for the second NNPF.

[0136] - CroppedHeight is set to be equal to nnpfcOutputPicHeight as defined for the second NNPF.

[0137] - Otherwise, the following applies:

[0138] - CroppedWidth is set to equal to pps_pic_width_in_luma_samples for currPic - SubWidthC (pps_conf_win_left_offset + pps_conf_win_right_offset) value.

[0139] - CroppedHeight is set to equal to pps_pic_height_in_luma_samples for currPic - SubHeightC The value of (pps_conf_win_top_offset + pps_conf_win_bottom_offset).

[0140] - For each value i in the range of 0 to numInputPics - 1 (inclusive), the luminance sample array CroppedYPic[i] and the chrominance sample arrays CroppedCbPic[i] and CroppedCrPic[i] (if present) are derived as follows:

[0141] - The variable sourcePic is derived as follows:

[0142] - If inputPresentFlag[i] equals 1 or nnpfc_absent_input_pic_zero_flag equals 0, then sourcePic is set to inputPic[i].

[0143] - Otherwise (inputPresentFlag[i] equals 0 and nnpfc_absent_input_pic_zero_flag equals 1), sourcePic is set to an image with a luminance sample array of CroppedWidth × CroppedHeight samples equal to 0 and a Cb and Cr sample array of (CroppedWidth / SubWidthC) × (CroppedHeight / SubHeightC) samples equal to 0.

[0144] - If numInputPics equals 1, then the following applies:

[0145] - The luminance sample array CroppedYPic[i] and the chrominance sample arrays CroppedCbPic[i] and CroppedCrPic[i] (if present) are set as two-dimensional arrays of the decoded sample values ​​of the Y, Cb and Cr components of sourcePic, respectively.

[0146] - Otherwise (numInputPics is greater than 1), the following applies:

[0147] - The variable sourceWidth is set to equal pps_pic_width_in_luma_samples for sourcePic - SubWidthC (pps_conf_win_left_offset + pps_conf_win_right_offset) value.

[0148] - The variable sourceHeight is set to equal pps_pic_height_in_luma_samples for sourcePic - SubHeightC The value of (pps_conf_win_top_offset + pps_conf_win_bottom_offset).

[0149] - If sourceWidth equals CroppedWidth and sourceHeight equals CroppedHeight, then resampledPic is set to be the same as sourcePic.

[0150] - Otherwise (sourceWidth is not equal to CroppedWidth or sourceHeight is not equal to CroppedHeight), the following applies:

[0151] - An NNPF must exist, hereinafter referred to as the super-resolution NNPF, which is defined by at least one NNPFC SEI message, activated by an NNPFA SEI message for the sourcePic, and has an nnpfc_purpose equal to 4, an nnpfcOutputPicWidth equal to CroppedWidth, and an nnpfcOutputPicHeight equal to CroppedHeight.

[0152] - resampledPic is set as the output of the neural network inference of the super-resolution NNPF, with sourcePic as the input.

[0153] - The luminance sample array CroppedYPic[i] and the chrominance sample arrays CroppedCbPic[i] and CroppedCrPic[i] (if present) are set as two-dimensional arrays of the decoded sample values ​​of the Y, Cb and Cr components of the resampledPic, respectively.

[0154] - BitDepth Y and BitDepth C All of them are set to equal BitDepth.

[0155] - ChromaFormatIdc is set to equal sps_chroma_format_idc.

[0156] - For all values ​​of i in the range from 0 to numInputPics - 1 (inclusive), the array StrengthControlVal[i] for the input image of NNPF is derived as follows:

[0157] - StrengthControlVal[i] is set to equal to (firstSliceQp) YThe value of (63 + QpBdOffset) ÷ (63 + QpBdOffset) is given by firstSliceQp. Y The SliceQp of the first slice equal to inputPic[i] Y .

[0158] No more than two NNPFC SEI messages with the same nnpfc_id value should exist in a single picture unit. If two NNPFC SEI messages with the same nnpfc_id value exist in a picture unit, these SEI messages must have different content. If two NNPFC SEI messages with the same nnpfc_id but different content exist in the same picture unit, these two NNPFC SEI messages must be in the same SEI NAL unit.

[0159] 4. The technical problem solved by the disclosed technical solution

[0160] The example design of the post-processing filter using SEI messages has the following problems:

[0161] First, there exists only a general post-processing filtering procedure that uses the specified NNPF, while there are also PPFs that are not NNPF.

[0162] Second, apart from special cases of PPF cascading, there is a lack of post-processing filtering for cascaded NNPFs. The special cases of PPF cascading occur when two PPFs are activated for the current image: both PPFs are NNPFs, one NNPF has an nnpfc_purpose equal to 4 and the other NNPF has multiple input images, and neither NNPF is associated with the SEI processing order SEI message.

[0163] Third, the list of output images from the post-processing filtering process cannot include: a cropped decoded image that does not have the corresponding output image output by any applied PPF, or a PPF output image output by a PPF that is not the last applied PPF when the specific image is the current image.

[0164] 5. List of solutions and implementation examples

[0165] To address the aforementioned issues, the methods outlined below are disclosed. These aspects should be considered as examples for interpreting general concepts, and not interpreted in a narrow sense. Furthermore, these examples can be applied individually or combined in any way.

[0166] 1) To solve the first problem, one or more of the following methods are specified:

[0167] a. In one example, a general post-processing filtering procedure using post-processing filters (PPF) (including but not limited to NNPF) is specified.

[0168] b. In one example, PPFs are grouped, and the PPF groups are interchangeable, so that for any given image, only one PPF group can be selected to apply.

[0169] c. In one example, the PPFs within the selected PPF group are applied in a cascaded manner, such that the output of one PPF is used as the input of the next PPF to be applied.

[0170] d. In one example, the indication of which PPFs to group can be obtained by signaling or by implicit deduction.

[0171] i. In one example, the group information of the activated PPF can be transmitted via signaling, such as in the order in which the PPFs are processed.

[0172] ii. In one example, an implicit group is defined as the case where two PPFs are activated for an image: both PPFs are NNPFs (i.e., the payloadType value for the NNPF indicates the neural network post-processing filter feature SEI message), one of the NNPFs has an nnpfc_purpose equal to 4 and the other NNPF has multiple input images, and neither NNPF is associated with the SEI processing order SEI message. In this case, the two NNPFs are implicitly considered to belong to one PPF group.

[0173] 2) To address the second problem, one or more of the following methods are specified:

[0174] a. In one example, regardless of how many PPFs are applied to the current image in the selected PPF group, and regardless of what type of PPFs they are, an image output by an earlier applied PPF is allowed to be used as an input image by a later applied PPF.

[0175] b. In one example, the list CandInputPicList, which includes all candidates for the input image, is initialized or reset to contain a list of cropped decoded images generated from the decoding BitstreamToFilter in output order for each current image before the first PPF is applied to the current image, and CandInputPicList is updated each time a PPF is applied, possibly except for the last PPF applied to the current image.

[0176] i. In one example, after applying PPF to the current image, the list CandInputPicList is updated by replacing each image in the list with the corresponding PPF output image.

[0177] 1. Optionally, in one example, before applying PPF to the current image, the list CandInputPicList is updated by replacing each image in the list that has a corresponding PPF output image and is in the order of output preceding the current image with that corresponding PPF output image.

[0178] ii. In one example, after applying PPF to the current image, the list CandInputPicList is updated by inserting the interpolated image (if any) into the list and placing the interpolated image such that all images in the updated list are in the output order.

[0179] iii. In one example, after applying a PPF to the current image, the list CandInputPicList is updated by replacing each image in the list with the corresponding PPF output image, inserting the interpolated image (if any) into the list, and placing the interpolated image so that all images in the updated list are arranged in output order.

[0180] iv. In one example, when an image in the list CandInputPicList is replaced, the image's properties (including at least one or more of the following, for example, as part of the list) are also updated:

[0181] 1. Image width in units of luminance samples

[0182] 2. Image height in units of brightness samples

[0183] 3. Bit depth of the brightness sample array for the image

[0184] 4. Bit depth for the chroma sample array of the image (if any).

[0185] 5. Image chroma format indicator

[0186] v. In one example, when an image is inserted into the list CandInputPicList, the image's attributes (including at least one or more of the following) are also stored, for example, as part of the list:

[0187] 1. Image width in units of luminance samples

[0188] 2. Image height in units of brightness samples

[0189] 3. Bit depth of the brightness sample array for the image

[0190] 4. Bit depth for the chroma sample array of the image (if any).

[0191] 5. Image chroma format indicator

[0192] 3) To address the third problem, one or more of the following methods are specified:

[0193] a. In one example, the output of the general post-processing filtering procedure is specified as a list of output images, ListOutputPics, which may include multiple images output by the last applied PPF.

[0194] i. In one example, the list ListOutputPics may include cropped, decoded images that do not have the corresponding output images from the PPF output of any application.

[0195] ii. In one example, the list ListOutputPics can include PPF output images when a particular image is the current image, produced by a PPF output that is not the last PPF applied.

[0196] iii. In one example, before any PPF is applied, the list ListOutputPics is initialized to contain a list of cropped decoded images produced from the decoder BitstreamToFilter in output order, and the list ListOutputPics is updated each time a PPF is applied.

[0197] 1. In one example, after a PPF is applied, the list ListOutputPics is updated by replacing each image in the list with the corresponding PPF output image.

[0198] 2. In one example, after PPF is applied, the list ListOutputPics is updated by inserting the interpolated image (if any) into the list and placing the interpolated image such that all images in the updated list are in the output order.

[0199] 3. In one example, after the PPF is applied, the list ListOutputPics is updated by replacing each image in the list with the corresponding PPF output image, inserting the interpolated image (if any) into the list, and placing the interpolated image so that all images in the updated list are arranged in output order.

[0200] iv. In one example, when an image in the list ListOutputPics is replaced, the image's properties (including at least one or more of the following, for example, as part of the list) are also updated:

[0201] 1. Image width in units of luminance samples

[0202] 2. Image height in units of brightness samples

[0203] 3. Bit depth of the brightness sample array for the image

[0204] 4. Bit depth for the chroma sample array of the image (if any).

[0205] 5. Image chroma format indicator

[0206] v. In one example, when an image is inserted into the list ListOutputPics, the image's properties (including at least one or more of the following) are also stored, for example, as part of the list:

[0207] 1. Image width in units of luminance samples

[0208] 2. Image height in units of brightness samples

[0209] 3. Bit depth of the brightness sample array for the image

[0210] 4. Bit depth for the chroma sample array of the image (if any).

[0211] 5. Image chroma format indicator

[0212] 4) In one example, based on any one or more of the above items, the PPF group is also referred to as the PPF processing chain or simply the processing chain.

[0213] 5) In one example, based on any one or more of the above items, the PPF may be indicated by an SEI message that indicates a post-processing operation and the payloadType value for that SEI message is included in the list SeiProcessingOrderSeiList, which is specified in the semantics of the SEI Processing Order (SPO) SEI message.

[0214] 6) In one example, based on any or more of the above items, specify that after applying PPF, the lists CandInputPicList and ListOutputPics should be updated in the same way: 1) replace each image in the list with the corresponding PPF output image of the PPF, and 2) insert the interpolated or extrapolated images (if any) into the list, and place the interpolated or extrapolated images such that all images in the updated list are arranged in the output order.

[0215] 6. Examples

[0216] The following are some example implementations of the aspects outlined in Section 5 of the previous article.

[0217] Most of the relevant sections that have been added or modified are shown in bold, and some of the deleted sections are shown in both bold and italic fonts. There may be some other changes that are editable in nature and therefore not indicated. These changes are based on JVET-AE2005, JVET-AE2006, and JVET-AE2027.

[0218] 6.1 Example 1

[0219] This embodiment refers to the following items outlined in Section 5 of the previous article: 1.a, 1.b, 1.c, 2.a, 2.b, 2.b.iii, 3.a, 3.ai, 3.a.ii, 3.a.iii, 3.a.iii.3.

[0220] 8.28.1 Using NNPF: A General Post-Processing Filtering Procedure Using PPF

[0221] 8.28.1.1 Overview

[0222] The input to this process is a bitstream, BitstreamToFilter. The output is a list of NNPF output images, ListNnpfOutputPics.

[0223] First, BitstreamToFilter is decoded, the list CroppedDecodedPictures is set to a list of cropped decoded images generated from decoding BitstreamToFilter in output order, and the list ListOutputPics is initialized to be the same as CroppedDecodedPictures.

[0224] Secondly, for each cropped and decoded image in CroppedDecodedPictures and for each of one or more NNPF PPF groups that are activated, and only one group is selected for application, the filtering process for an image as specified in sub-entry 8.28.1.2 is repeatedly called in the order of output.

[0225] For each current image, multiple PPFs can be activated, and these PPFs can belong to one or more PPF groups. PPF groups are interchangeable; that is, at most one group can be selected for application. Except for special PPF cascading cases, each PPF group containing multiple PPFs is associated with an SEI message for the SEI processing order, which has a specific value for `po_id`. A special PPF cascading case occurs when two PPFs are activated for the current image: both PPFs are NNPFs, one NNPF has an `nnpfc_purpose` equal to 4, and the other NNPF has multiple input images, and neither NNPF is associated with an SEI message for the SEI processing order. In this case, the two NNPFs are implicitly considered to belong to one PPF group. Except for special PPF cascading cases, any PPF not associated with an SEI message for the SEI processing order resides in its own PPF group. One or more PPFs from the selected PPF group can be applied. When multiple PPFs are applied (within the selected PPF group), they are applied in a cascading manner, which means that they are applied in the order indicated by the SEI processing order message associated with the selected PPF group, and for each PPF that is not the last PPF applied, the output is used as the input of the next PPF applied.

[0226] The order of the images in ListNnpfOutputPics is the output order.

[0227] Within ListNnpfOutputPics, no more than one image should be associated with any particular output time instance. When multiple NNPFs and multiple PPF groups are active for any particular image in CroppedDecodedPictures, and although any NNPF can be selected, only one of the multiple NNPFs is allowed to be applied, the above constraint applies regardless of which NNPF is applied to which group of PPFs is selected for that particular image, when that particular image is the current image.

[0228] For any specific pair of images, inputPicA and inputPicB, consecutive in output order within CroppedDecodedPictures, if one or more images from ListNnpfOutputPicsListOutputPicsinterpolatedPicSetA exist between inputPicA and inputPicB in output order, the images in interpolatedPicSetA must be one of the images output when the specific image currPicA in CroppedDecodedPictures is the current image by applying a specific NNPF nnpfA PPF ppfA with PictureRateUpsamplingFlag equal to 1. No other NNPF PPF (including nnpfA) or PPF (including ppfA) used in the filtering process for an image when currPicA is the current image, or any NNPF (including nnpfA) or PPF (including ppfA) used in the filtering process for an image when any other image currPicB in CroppedDecodedPictures is the current image, should be output between inputPicA and inputPicB in output order.

[0229] Note: The intent of the constraint expressed in the above paragraph is to prohibit generating an NNPFPPF output image more than once between any given consecutive input image pairs.

[0230] 8.28.1.2 Filtering process for an image

[0231] The filtering procedure specified in this entry applies to each cropped decoded picture (referred to as the current picture) in CroppedDecodedPictures that activates one or more PPF groups, selects only one PPF group to apply, and the number of PPFs to be applied (in the selected PPF group) is greater than 0.

[0232] The filtering procedure for an image using a single PPF, as specified in sub-entry 8.28.1.3, is called repeatedly for each PPF to be applied. When the number of PPFs to be applied is greater than one, the following applies:

[0233] - If a special PPF cascade case applies to the selected PPF group, the NNPF with nnpfc_purpose equal to 4 is applied first, followed by the NNPF with multiple input images.

[0234] - Otherwise (the special PPF cascading case does not apply to the selected PPF group), the PPFs are applied in the preferred order indicated by the SEI message, according to the SEI processing order associated with the selected PPF group.

[0235] 8.28.1.2 Filtering process for an image using NNPF

[0236] 8.28.1.3 Filtering process for an image using a single PPF

[0237] When a particular image is the current image and a particular PPF is applied, the filtering process specified in this entry is applied to CroppedDecodedPictures and each cropped decoded image (referred to as the current image) is activated for one or more NNPFs.

[0238] Before applying a PPF, when this PPF is the first PPF to be applied, the list CandInputPicList is set to be the same as CroppedDecodedPictures.

[0239] When a PPF is applied to the current image, the input image for the PPF is selected from the list CandInputPicList, and the images generated and output by the PPF are in the same order as the output images.

[0240] When applying a PPF (Power over Filter) to the current image using NNPF, the following applies:

[0241] - The filtered and / or interpolated images are generated by NNPF by applying the NNPF procedures specified in the semantics of the NNPFC SEI message to the current image in a block-by-block manner.

[0242] - The order in which images are generated by NNPF by applying the NNPF process, which is stored in the output tensor of NNPF, is the output order.

[0243] When the applied NNPF is the last NNPF applied to the current image, the images generated by the NNPF and output by the NNPF process are included in ListNnpfOutputPics, in the same order as when the images are stored in the output tensor of the NNPF.

[0244] After applying PPF, update the lists CandInputPicList and ListOutputPics in the same way: 1) replace each image in the list with the corresponding PPF output image, and 2) insert the interpolated images (if any) into the list and place the interpolated images so that all images in the updated list are arranged in the output order.

[0245] 8.28.2.2 Characteristics of Neural Network Post-Processing Filters and Semantics of SEI Messages

[0246] The Neural Network Post-Processing Filter Characteristics (NNPFC) SEI message specifies the neural networks that can be used as post-processing filters. For a specific image, the specified use of a Neural Network Post-Processing Filter (NNPF) is indicated by the Neural Network Post-Processing Filter Activation (NNPFA) SEI message.

[0247] The following variables need to be specified when using this SEI message:

[0248] - A list called CandInputPicList, which contains a list of images in output order, from which you select the input image for NNPF.

[0249] Note 1 - This list is updated each time a PPF is applied to the current image, through the PPF filtering process, unless that PPF is the last PPF applied to the current image.

[0250] - Input image width and height in units of brightness samples, denoted as CroppedWidth and CroppedHeight in this paper, respectively.

[0251] - The luminance sample array CroppedYPic[idx] and chrominance sample arrays CroppedCbPic[idx] and CroppedCrPic[idx] (if present) of the input image, with index idx ranging from 0 to numInputPics - 1 (inclusive), are used as input to NNPF.

[0252] - BitDepth of the luminance sample array for the input image Y .

[0253] - BitDepth of the chroma sample array (if any) for the input image C .

[0254] - Chroma format indicator, referred to herein as ChromaFormatIdc, as described in sub-entry 7.3.

[0255] - Enter the chroma format indicator ChromaFormatIdc for the image, as described in sub-entry 7.3.

[0256] - When nnpfc_auxiliary_inp_idc equals 1, the filter strength control value array StrengthControlVal[idx] must contain real numbers in the range of 0 to 1 (inclusive) for the input image with index idx ranging from 0 to numInputPics - 1 (inclusive).

[0257] The input image at index 0 corresponds to the image in CandInputPicList that is activated by the NNPFA SEI message for the NNPF defined by the NNPFC SEI message. Input images with indices ranging from 1 to numInputPics - 1 (inclusive) precede the input images at index i - 1 in the output order.

[0258] Note 2 - The image corresponding to the image in CandInputPicList is either the cropped decoded output image of that image or a filtered version of the cropped decoded output image of the previously applied PPF.

[0259] The variables SubWidthC and SubHeightC are derived from ChromaFormatIdc, as specified in Table 2.

[0260] …

[0261] `nnpfc_absent_input_pic_zero_flag` equal to 1 indicates that NNPF expects the input image corresponding to an image that does not exist in the bitstream to be represented by an array of samples with sample values ​​equal to 0. `nnpfc_absent_input_pic_zero_flag` equal to 0 indicates that the input image `inputPicA` corresponding to an image that NNPF expects to not exist in the bitstream is represented by the input image `inputPicB`, which is the closest to `inputPicA` in the output order and whose corresponding image exists in the bitstream.

[0262] …

[0263] `nnpfa_no_prev_clvs_flag` equal to 1 indicates that the input image for NNPF does not originate from a previous CLVS. `nnpfa_no_prev_clvs_flag` equal to 0 indicates that the input image for NNPF may or may not originate from a previous CLVS.

[0264] Note 4 - The value of nnpfa_no_prev_clvs_flag can change from 0 to 1 when the current CLVS is spliced ​​from another bitstream adjacent to the previous CLVS, and the NNPFA SEI message will cause one or more input images with corresponding images to be selected from one or more previous CLVS, and thus may have a negative impact on the output of the target NNPF.

[0265] The value of nnpfa_no_foll_clvs_flag equal to 1 indicates that when the NNPFA SEI message persists for the last PU of the CLVS in output order, the NNPFA SEI message is treated as if it persisted for the last PU of the current layer within the bitstream in output order. When the NNPFA SEI message does not persist for the last PU of the CLVS in output order, or when nnpfa_no_foll_clvs_flag equals 0, the value of nnpfa_no_foll_clvs_flag has no specific effect.

[0266] Note 5 - When subsequent CLVSs are concatenated from different bitstreams adjacent to the current CLVS, the value of nnpfa_no_foll_clvs_flag can change from 0 to 1 for image rate upsampling NNPF. Therefore, the NNPF process interpolates the image to the end of the current CLVS using only the input image corresponding to the image from the current CLVS.

[0267] …

[0268] D.11 SEI Processing Order SEI Messages

[0269] D.11.1 SEI Processing Order SEI Message Syntax

[0270]

[0271] D.11.2 SEI Processing Order and SEI Message Semantics

[0272] SEI Processing Order: SEI messages carry information indicating the preferred processing order for groups of different types of SEI messages that can exist in CVS and can be applied in a cascading manner, as determined by the encoder (i.e., the content producer).

[0273] Note 1 - In the semantics of this SEI message, two different types of SEI messages can have the same SEIpayloadType value, but are distinguished by some syntax elements in the SEI payload. For example, two Neural Network Post-Processing Filter Feature (NNPFC) SEI messages with different nnpfc_id values ​​are considered to be two different types of SEI messages.

[0274] When a Sequential SEI message with a specific po_id value exists in any access unit of the CVS, it must also exist in the first access unit of the CVS. Sequential SEI messages continue from the current access unit in decoding order until the end of the CVS. When multiple Sequential SEI messages with the same po_id value exist in the CVS, they must have identical content.

[0275] The requirement for bitstream consistency is that within the SEI processing order SEI message, there must be at least two pairs of syntax elements po_sei_payload_type[i] and po_sei_processing_order[i], and there must be at least two unequal po_sei_processing_order[i] values.

[0276] SEI processing order: SEI messages can carry one or more SEI prefix indicators for a specific payloadType. Each SEI prefix indicator is a byte string that follows the SEI payload syntax according to the value of that payloadType, and contains the number of complete syntax elements starting from the first syntax element in the SEI payload, and may be followed by bits that do not represent any complete syntax elements of the SEI payload.

[0277] These SEI prefixes must provide sufficient information to determine the specific processing order of SEI messages that have the same payloadType value but different preferred processing orders.

[0278] `po_id` contains an identifier for a group of SEI message types. For a group of this SEI message type, the preferred processing order is indicated in the SEI processing order message. The value of `po_id` must be between 0 and 2. 32 - The range is 2 (inclusive). The value of po_id is from 256 to 511 (inclusive) and from 2... 31 Up to 2 32 - 2 (inclusive of end value) is reserved for future use by ITU-T | ISO / IEC. Decoders conforming to this document of this version encounter po_id in the range of 256 to 511 (inclusive of end value) or 2.31 Up to 2 32 When processing SEI messages in the range of -2 (inclusive), the SEI message must be ignored.

[0279] The post-processing filter (PPF) can be indicated by an SEI message, for which the payloadType value is specified in the SeiProcessingOrderSeiList below.

[0280] For each image, multiple PPFs can be activated, and these PPFs can belong to one or more PPF groups. PPF groups are interchangeable; that is, at most one group can be selected for application.

[0281] A special case of PPF cascading is defined as the situation where two PPFs are activated for an image: both PPFs are NNPFs (i.e., the payloadType value for the NNPF indicates the neural network post-processing filter feature SEI message), one of the NNPFs has an nnpfc_purpose of 4 and the other NNPF has multiple input images, and neither NNPF is associated with the SEI message processing order. In this case, the two NNPFs are implicitly considered to belong to a PPF group, and the NNPF with an nnpfc_purpose of 4 is applied first.

[0282] Except for special PPF cascading cases, each PPF group containing multiple PPFs is associated with an SEI message in the SEI processing order, which has a specific value of po_id. Any PPF not associated with an SEI message in the SEI processing order, except for special PPF cascading cases, resides in its own PPF group.

[0283] One or more PPFs from the selected PPF group can be applied. When multiple PPFs are applied (within the selected PPF group), they are applied in a cascading manner, which means that they are applied in the order indicated by the SEI processing order message associated with the selected PPF group, and for each PPF that is not the last PPF applied, the output is used as the input of the next PPF applied.

[0284] po_num_sei_messages_minus2 plus 2 indicates the number of SEI messages, which have the processing order indicated in the SEI processing order message.

[0285] po_sei_importance_flag[i] indicates the importance of the SEI message at index i, as determined by the encoder.

[0286] If the decoding system cannot interpret or does not support any SEI message with a po_sei_importance_flag[i] equal to 1, then the entire SEI processing order SEI message must be ignored.

[0287] po_alignment_zero_bit must be equal to 0.

[0288] If po_sei_wrapping_flag[i] equals 0, then the SEI message must exist outside the SEI processing order SEI message with payloadType equal to po_sei_payload_type[i]. However, if po_sei_wrapping_flag[i] equals 0 and no SEI message with payloadType equal to po_sei_payload_type[i] exists, then the following applies:

[0289] - If po_sei_importance_flag[i] equals 1, the decoder must ignore the entire SEI processing order SEI message.

[0290] Otherwise, the decoder must ignore all data associated with the loop variable value of i.

[0291] Note 2 - `po_sei_wrapping_flag[i]` equal to 1 allows SEI messages to be carried within SEI messages processed in the SEI processing order, preventing such SEI messages from being misinterpreted by decoders that do not process SEI messages processed in the SEI processing order. Therefore, `po_sei_wrapping_flag[i]` equal to 1 is intended to be used when `po_sei_wrapping_flag[i]` equal to 0 would cause such decoders to produce unexpected results.

[0292] A value of 1 for po_sei_prefix_flag[i] indicates that po_num_prefix_bytes[i] exists. A value of 0 for po_sei_prefix_flag[i] indicates that po_num_prefix_bytes[i] does not exist.

[0293] `po_sei_payload_type[i]` specifies the `payloadType` value for the `i`-th SEI message type, providing preferred processing order information in the SEI message for that `i`-th SEI message type. For any two distinct non-negative integer values ​​`m` and `n`, the values ​​of `po_sei_payload_type[m]` and `po_sei_payload_type[n]` should not be the same unless both `po_sei_prefix_flag[m]` and `po_sei_prefix_flag[n]` are equal to 1.

[0294] SeiProcessingOrderSeiList is set to consist of payloadType values ​​as specified in entry D.2.1, except for the values ​​137, 144, 147, 148, 179, 180, 200, 201, 208, and 213. When po_sei_payload_type[i] is not equal to any value in SeiProcessingOrderSeiList, the value of po_sei_prefix_flag[i] must be equal to 0.

[0295] When present, po_num_prefix_bytes_minus1[i] increments by 1 to specify the number of bytes associated with the i-th SEI message, for which the preferred processing order information is provided in the SEI processing order message.

[0296] po_prefix_byte[i][j] (if it exists) specifies the value of the j-th byte of the i-th SEI message.

[0297] po_sei_processing_order[i] indicates the preferred processing order for the i-th SEI message type, and provides preferred processing order information in the SEI processing order SEI message for the i-th SEI message type. For any two distinct integer values ​​m and n greater than or equal to 0, po_sei_processing_order[m] less than po_sei_processing_order[n] indicates that any SEI message type with payloadType equal to po_sei_payload_type[m] and (if present) bytes po_prefix_byte[m][p] in the range of 0 to po_num_prefix_bytes[m] - 1 (inclusive) must be processed before any SEI message type with payloadType equal to po_sei_payload_type[n] and (if present) bytes po_prefix_byte[n][q] in the range of 0 to po_num_prefix_bytes[n] - 1 (inclusive) and po_sei_processing_order[m] equal to po_sei_processing_order[n] indicates that there is no preferred processing order among the SEI message types. When multiple SEI messages exist and the values ​​of po_sei_payload_type[i], po_num_prefix_bytes[i], and byte po_prefix_byte[i][j] (j ranges from 0 to po_num_prefix_bytes[i] - 1, inclusive) are the same, they must have the same po_sei_processing_order[i].

[0298] po_sei_processing_order[0] must be equal to 0, and for i greater than 0, po_sei_processing_order[i] must be equal to po_sei_processing_order[i-1] or po_sei_processing_order[i-1]+1.

[0299] The value of po_sei_processing_order[ po_num_sei_messages_minus2 + 1 ] should not be equal to 0.

[0300] D.12.11 Includes the use of post-processing filter SEI messages, including neural network post-processing filter characteristic SEI messages and neural network post-processing filter activation SEI messages.

[0301] Post-processing filters (PPFs) can be indicated via SEI messages, for which the payloadType value is in SeiProcessingOrderSeiList, which is specified in the semantics of the SEI message regarding the SEI processing order.

[0302] Let currPic be the cropped decoded output image. For this cropped decoded output image, activate the post-processing filter (PPF) defined by the neural network post-processing filter property (NNPFC) SEI message through, for example, the neural network post-processing filter (NNPF), and let currLayerId be the nuh_layer_id value of currPic.

[0303] The list `candInputPicList` contains a list of images ordered by output, from which you select the input image for the PPF.

[0304] Note 1 - This list is updated each time a PPF is applied to the current image, through the PPF filtering process, unless that PPF is the last PPF applied to the current image.

[0305] When the PPF is not an NNPF, the PPF is considered to have only one input image, which is the image in candInputPicList corresponding to the current image.

[0306] Note 2 - The image corresponding to the cropped decoded output image in candInputPicList is either the cropped decoded output image itself or a filtered version of the cropped decoded output image that was previously used as the output image of the PPF.

[0307] If the PPF is the first PPF applied to the current image, then the following applies:

[0308] - CroppedWidth is set to equal to pps_pic_width_in_luma_samples for currPic - SubWidthC (pps_conf_win_left_offset + pps_conf_win_right_offset) value.

[0309] - CroppedHeight is set to equal to pps_pic_height_in_luma_samples for currPic - SubHeightC The value of (pps_conf_win_top_offset + pps_conf_win_bottom_offset).

[0310] - BitDepth Y and BitDepth C All of them are set to equal BitDepth.

[0311] - ChromaFormatIdc is set to equal sps_chroma_format_idc.

[0312] Otherwise (if the PPF is not the first PPF applied to the current image), the following applies:

[0313] - CroppedWidth is set to equal the width of the image in candInputPicList corresponding to the current image, in luminance samples.

[0314] - CroppedHeight is set to equal to the height of the image in candInputPicList corresponding to the current image, in units of luminance samples.

[0315] - BitDepth Y It is set to be equal to the bit depth (BitDepth) of the luminance sample array corresponding to the current image in candInputPicList. Y .

[0316] - BitDepth C The bit depth is set to equal to the bit depth of the chroma sample array (if any) of the image corresponding to the current image in candInputPicList. C .

[0317] - ChromaFormatIdc is set to be equal to the chroma format indicator ChromaFormatIdc of the image corresponding to the current image in candInputPicList.

[0318] The remainder of this entry applies when the PPF is an NNPF.

[0319] The requirement for bitstream consistency is that when a picture unit contains an NNPFA SEI message, the value of ph_pic_output_flag in the picture header contained in that picture unit must be equal to 1.

[0320] Note 3 - Since only the cropped decoded output image is used as the input image for NNPF when NNPF is the first PPF applied to currPic, the value of ph_pic_output_flag in the image header of the encoded / decoded image corresponding to each input image of NNPF is equal to 1.

[0321] The variable pictureRateUpsamplingFlag is set to equal to ( ( nnpfc_purpose & 0x08 ) >0 ) ? 1 : 0.

[0322] The variable numInputPics is set to equal nnpfc_num_input_pics_minus1 + 1.

[0323] The variable numInferences is derived as follows:

[0324] - If all of the following conditions are true, then the variable numPostRoll is set to the value of i that makes nnpfc_interpolated_pics[i] greater than 0, and the variable numInferences is set to 1 + numPostRoll:

[0325] - nnpfc_purpose equals 8 (i.e., the sole purpose of NNPF is image rate upsampling).

[0326] - nnpfa_persistence_flag equals 1.

[0327] - Only for a single i value greater than 0, nnpfc_interpolated_pics[i] is greater than 0.

[0328] - Any of the following conditions is true:

[0329] - currPic is the last picture in the output order of the bitstream with nuh_layer_id equal to currLayerId.

[0330] - currPic is the last image in the CLVS in the output order, and nnpfa_no_foll_clvs_flag is equal to 1.

[0331] - Otherwise, if all of the following conditions are true, the variable numPostRoll is set to equal InpIdx[i], where the value of i makes nnpfa_output_flag[i] equal to 1, and the variable numInferences is set to equal 1 + numPostRoll:

[0332] - pictureRateUpsamplingFlag equals 0.

[0333] - numInputPics is greater than 1.

[0334] - nnpfa_persistence_flag equals 1.

[0335] - For a single idx value in the range of 0 to NumInpPicsInOutputTensor - 1 (inclusive), nnpfa_output_flag[idx] is equal to 1, and for that single idx value, InpIdx[idx] is greater than 0.

[0336] - Any of the following conditions is true:

[0337] - currPic is the last picture in the output order of the bitstream with nuh_layer_id equal to currLayerId.

[0338] - currPic is the last image in the CLVS in the output order, and nnpfa_no_foll_clvs_flag is equal to 1.

[0339] Otherwise, the variable numInferences is set to 1.

[0340] For each value of j in the range 0 to numInferences - 1 (inclusive), the following derivation applies to the input images of NNPF, such that each input image is an image in candInputPicList:

[0341] The arrays inputPic[i] and inputPresentFlag[i] (which represent all input images and the existence of input images, respectively) in the range of 0 to numInputPics - 1 (inclusive) are defined as follows:

[0342] - When j is greater than 0, for each k value in the range of 0 to j - 1 (inclusive), inputPic[k] is set to the image in candInputPicList corresponding to currPic, and inputPresentFlag[k] is set to equal to 0.

[0343] - The j-th input image inputPic[j] is set to the image corresponding to currPic in candInputPicList, and inputPresentFlag[j] is set to 1.

[0344] - When numInputPics is greater than 1, for each value of i in the range from j + 1 to numInputPics - 1 (inclusive), sorted in ascending order of i, the following applies:

[0345] - If both of the following conditions are true, then inputPic[i] is set to the image corresponding to prevPic in candInputPicList, and inputPresentFlag[i] is set to 1:

[0346] - Any of the following conditions is true:

[0347] - pictureRateUpsamplingFlag equals 1, and currPic is associated with a frame packing arrangement SEI message having a specific value of frame_packing_arrangement_type equal to 5 and fp_current_frame_is_frame0_flag, and there exists a cropped decoded output image prevPic, which is the last image in output order among all cropped decoded output images. All cropped decoded output images have a nuh_layer_id equal to currLayerId, are in output order before inputPic[i-1], and are associated with a frame packing arrangement SEI message having the same value of frame_packing_arrangement_type equal to 5 and fp_current_frame_is_frame0_flag.

[0348] - if pictureRateUpsamplingFlag is equal to 0 or currPic is not associated with a frame packing arrangement SEI message with frame_packing_arrangement_type equal to 5, and there exists a cropped decoded output image prevPic, which is the last image in output order among all cropped decoded output images, and all cropped decoded output images have nuh_layer_id equal to currLayerId and are before inputPic[i - 1] in output order.

[0349] - nnpfa_no_prev_clvs_flag equals 0, or the encoded / decoded image corresponding to prevPic and the current image exist in the same CLVS.

[0350] - Otherwise, the following applies:

[0351] - inputPic[i] is set to the same image as inputPic[i-1], and inputPresentFlag[i] is set to 0.

[0352] - The requirement for bitstream consistency is that when pictureRateUpsamplingFlag is equal to 1, nnpfc_interpolated_pics[i-1] must be equal to 0.

[0353] - The requirement for bitstream consistency is that when inputPresentFlag[i] equals 0 and nnpfc_input_pic_output_flag[i] equals 1, for the value of idx that makes InpIdx[idx] equal to i, the value of nnpfa_output_flag[idx] must be equal to 0.

[0354] - To interpret NNPFC SEI messages, the following variables are specified:

[0355] - If numInputPics is greater than 1 and there exists a second NNPF defined by at least one NNPFC SEI message, activated by an NNPFA SEI message for currPic, and having an nnpfc_purpose equal to 4, then the following applies:

[0356] - CroppedWidth is set to be equal to nnpfcOutputPicWidth as defined for the second NNPF.

[0357] - CroppedHeight is set to be equal to nnpfcOutputPicHeight as defined for the second NNPF.

[0358] - Otherwise, the following applies:

[0359] - CroppedWidth is set to equal to pps_pic_width_in_luma_samples for currPic - SubWidthC (pps_conf_win_left_offset + pps_conf_win_right_offset) value.

[0360] - CroppedHeight is set to equal to pps_pic_height_in_luma_samples for currPic - SubHeightC The value of (pps_conf_win_top_offset + pps_conf_win_bottom_offset).

[0361] - For each value i in the range of 0 to numInputPics - 1 (inclusive), the luminance sample array CroppedYPic[i] and the chrominance sample arrays CroppedCbPic[i] and CroppedCrPic[i] (if they exist) are derived as follows:

[0362] - The variable sourcePic is derived as follows:

[0363] - If inputPresentFlag[i] equals 1 or nnpfc_absent_input_pic_zero_flag equals 0, then sourcePic is set to inputPic[i].

[0364] - Otherwise (inputPresentFlag[i] equals 0 and nnpfc_absent_input_pic_zero_flag equals 1), sourcePic is set to an image with a luminance sample array of CroppedWidth × CroppedHeight samples equal to 0 and a Cb and Cr sample array of (CroppedWidth / SubWidthC) × (CroppedHeight / SubHeightC) samples equal to 0.

[0365] - If numInputPics equals 1, then the following applies:

[0366] - The luminance sample array CroppedYPic[i] and the chrominance sample arrays CroppedCbPic[i] and CroppedCrPic[i] (if present) are set as two-dimensional arrays of the decoded sample values ​​of the Y, Cb and Cr components of sourcePic, respectively.

[0367] - Otherwise (numInputPics is greater than 1), the following applies:

[0368] - The variable sourceWidth is set to equal pps_pic_width_in_luma_samples for sourcePic - SubWidthC (pps_conf_win_left_offset + pps_conf_win_right_offset) value.

[0369] - The variable sourceHeight is set to equal pps_pic_height_in_luma_samples for sourcePic - SubHeightC The value of (pps_conf_win_top_offset + pps_conf_win_bottom_offset).

[0370] - If sourceWidth equals CroppedWidth and sourceHeight equals CroppedHeight, then resampledPic is set to be the same as sourcePic.

[0371] - Otherwise (sourceWidth is not equal to CroppedWidth or sourceHeight is not equal to CroppedHeight), the following applies:

[0372] - An NNPF must exist, hereinafter referred to as the super-resolution NNPF, which is defined by at least one NNPFC SEI message, activated by an NNPFA SEI message for the sourcePic, and has an nnpfc_purpose equal to 4, an nnpfcOutputPicWidth equal to CroppedWidth, and an nnpfcOutputPicHeight equal to CroppedHeight.

[0373] - resampledPic is set as the output of the neural network inference of the super-resolution NNPF, with sourcePic as the input.

[0374] - The luminance sample array CroppedYPic[i] and the chrominance sample arrays CroppedCbPic[i] and CroppedCrPic[i] (if present) are set as two-dimensional arrays of the decoded sample values ​​of the Y, Cb and Cr components of the resampledPic, respectively.

[0375] - BitDepth Y and BitDepth C All of them are set to equal BitDepth.

[0376] - ChromaFormatIdc is set to equal sps_chroma_format_idc.

[0377] - For all values ​​of i in the range from 0 to numInputPics - 1 (inclusive), the array StrengthControlVal[i], which specifies the filter strength control values ​​for the input image of NNPF, is derived as follows:

[0378] - StrengthControlVal[i] is set to equal to (firstSliceQp) Y The value of (63 + QpBdOffset) ÷ (63 + QpBdOffset) is given by firstSliceQp. Y Equals the SliceQp of the first strip of the decoded output image after cropping corresponding to inputPic[i]. Y .

[0379] No more than two NNPFC SEI messages with the same nnpfc_id value should exist in a single picture unit. If two NNPFC SEI messages with the same nnpfc_id value exist in a picture unit, these SEI messages must have different content. If two NNPFC SEI messages with the same nnpfc_id but different content exist in the same picture unit, these two NNPFC SEI messages must be in the same SEI NAL unit.

[0380] 6.2 Example 2

[0381] This embodiment refers to the items outlined in Section 5 of the previous article: 1.a, 1.b, 1.c, 2.a, 2.b, 2.b.iii, 3.a, 3.ai, 3.a.ii, 3.a.iii, 3.a.iii, 3, 4, 5 and 6.

[0382] 6.2.1 H.274 / VSEI Specification

[0383] Note that the following H.274 / VSEI specification is based on JVET-AG2034-v1 (publicly available here: https: / / www.jvet-experts.org / doc_end_user / documents / 33_Teleconference / wg11 / JVET-AG2034-v1.zip). The entries and sub-entries mentioned below are shown below. Entries and sub-entries not mentioned below are the same as those in JVET-AG2034-v1.

[0384] In item 4, add the following abbreviations:

[0385] PPF post-processing filter

[0386] SPO SEI processing order

[0387] Change the title of sub-entry 8.28 from "Neural Network Post-Processing Filter SEI Messages" to "General Post-Processing Filtering Procedure and Neural Network Post-Processing Filter SEI Messages".

[0388] Sub-entry 8.28.1 is modified as follows:

[0389] 8.28.1 General Post-Processing Filtering Procedure Using PPF

[0390] 8.28.1.1 Overview

[0391] The input to this process is a bitstream, BitstreamToFilter. The output is a list of PPF output images, ListPpfOutputPics.

[0392] A PPF can be indicated by an SEI message, which specifies the post-processing operation, and the payloadType value for that SEI message is included in the list SeiProcessingOrderSeiList, which is defined in the semantics of the SPO SEI message. For each image, multiple PPFs can be activated, and these PPFs can belong to one or more PPF processing chains. A PPF processing chain consists of a list of PPFs indicated by an SPOSEI message with a specific value of po_id. PPF processing chains are interchangeable; that is, at most one processing chain can be selected for application.

[0393] A special case of PPF cascading is defined as when two PPFs are activated for an image: both PPFs are NNPFs, one NNPF has an nnpfc_purpose of 4 and the other NNPF has multiple input images, and neither NNPF is associated with an SPO SEI message. In this case, the two NNPFs are implicitly considered to belong to a processing chain, and the NNPF with an nnpfc_purpose of 4 is applied first.

[0394] Except for special PPF cascading cases, each processing chain containing multiple PPFs is associated with an SPO SEI message having a specific value of po_id. Except for special PPF cascading cases, any PPF not associated with an SPO SEI message is in its own processing chain.

[0395] One or more PPFs from the selected processing chain can be applied. When multiple PPFs are applied (in the selected processing chain), they are applied in a cascading manner, meaning they are applied in the order indicated by the SPOSEI message associated with the selected processing chain, and for each PPF that is not the last PPF applied, the output is used as the input to the next PPF applied.

[0396] First, BitstreamToFilter is decoded, and the list CroppedDecodedPictures is set to a list of cropped decoded images generated from decoding BitstreamToFilter in output order, and the list ListPpfOutputPics is initialized to be the same as CroppedDecodedPictures.

[0397] Secondly, for each cropped decoded picture in CroppedDecodedPictures and for which one or more processing chains are activated and only one processing chain is selected for application, the filtering process for a picture as specified in Entry 8.28.1.2 is called repeatedly in the output order.

[0398] The order of the images in ListPpfOutputPics is the output order.

[0399] Within ListPpfOutputPics, no more than one image should be associated with any particular output time instance. When multiple processing chains of PPFs are active for any particular image in CroppedDecodedPictures, the above constraint must apply regardless of which processing chain is selected when the particular image is the current image.

[0400] For any given pair of images, inputPicA and inputPicB, consecutive in output order within CroppedDecodedPictures, if there are one or more images, intermediatePicSetA, in ListPpfOutputPics between inputPicA and inputPicB in output order, the images in intermediatePicSetA must be among the images output by applying a specific PPF, ppfA, when the given image currPicA in CroppedDecodedPictures is the current image. When all PPFs involved are NNPFs, one and only one of the following must be applied:

[0401] - The image in intermediatePicSetA must be one of the images output by applying a specific NNPF nnpfA with PictureRateUpsamplingFlag equal to 1 when a specific image currPicA in CroppedDecodedPictures is the current image.

[0402] - The image in intermediatePicSetA must be one of the images output by applying a specific NNPF nnpfA with TemporalExtrapolationFlag equal to 1 when a specific image currPicA in CroppedDecodedPictures is the current image.

[0403] When currPicA is the current image, the application of any other PPF used in the filtering process for an image, or the application of any PPF (including ppfA) used in the filtering process for an image when currPicB is the current image in CroppedDecodedPictures, should not output any images between inputPicA and inputPicB in output order. Note - The intent of the constraint expressed in the above paragraph is to prohibit generating PPF output images more than once between any particular consecutive input image pairs.

[0404] 8.28.1.2 Filtering process for an image

[0405] The filtering procedure specified in this entry applies to each cropped decoded picture (referred to as the current picture) in CroppedDecodedPictures and for each of which one or more processing chains are activated, only one processing chain is selected for application, and the number of PPFs to be applied (in the selected processing chain) is greater than 0.

[0406] The filtering procedure for an image using a single PPF, as specified in sub-entry 8.28.1.3, is called repeatedly for each PPF to be applied. When the number of PPFs to be applied is greater than one, the following applies:

[0407] - If a special PPF cascade case applies to the selected processing chain, the NNPF with nnpfc_purpose equal to 4 is applied first, followed by the NNPF with multiple input images.

[0408] - Otherwise (the special PPF cascading case does not apply to the selected processing chain), PPF is applied in the preferred order indicated by the SPO SEI message associated with the selected processing chain.

[0409] 8.28.1.3 Filtering process for an image using PPF

[0410] The filtering procedure specified in this entry applies when a specific image is the current image and a specific PPF is applied.

[0411] Before applying a PPF, when this PPF is the first PPF to be applied, the list CandInputPicList is set to be the same as CroppedDecodedPictures.

[0412] When a PPF is applied to the current image, the input image for the PPF is selected from the list CandInputPicList, and the images generated and output by the PPF are in the same order as the output images.

[0413] When applying a PPF (Power over Filter) to the current image using NNPF, the following applies:

[0414] - The filtered and / or interpolated image is generated by NNPF by applying the NNPF procedure specified in the semantics of the NNPFC SEI message to the current image in a block-by-block manner.

[0415] - The order in which images are generated by NNPF by applying the NNPF process, which is stored in the output tensor of NNPF, is the output order.

[0416] After applying PPF, update the lists CandInputPicList and ListOutputPics in the same way: 1) replace each image in the list with the corresponding PPF output image, and 2) insert the interpolated or extrapolated images (if any) into the list and place them so that all images in the updated list are in the output order.

[0417] The sub-entry 8.28.2.2 is modified as follows:

[0418] 8.28.2.2 Characteristics of Neural Network Post-Processing Filters and Semantics of SEI Messages

[0419] The Neural Network Post-Processing Filter Characteristics (NNPFC) SEI message specifies the neural networks that can be used as post-processing filters. For a specific image, the specified use of a Neural Network Post-Processing Filter (NNPF) is indicated by the Neural Network Post-Processing Filter Activation (NNPFA) SEI message.

[0420] The following variables need to be specified when using this SEI message:

[0421] - A list called CandInputPicList, which contains a list of images in output order, from which you select the input image for NNPF.

[0422] Note 1 - This list is updated each time a PPF is applied to the current image, through the PPF filtering process, unless that PPF is the last PPF applied to the current image.

[0423] - Input image width and height in units of brightness samples, denoted as CroppedWidth and CroppedHeight in this paper, respectively.

[0424] - The luminance sample array CroppedYPic[idx] and chrominance sample arrays CroppedCbPic[idx] and CroppedCrPic[idx] (if present) of the input image, with index idx ranging from 0 to numInputPics - 1 (inclusive), are used as input to NNPF.

[0425] - BitDepthY for the luminance sample array of the input image.

[0426] - BitDepthC for the chroma sample array of the input image (if any).

[0427] - Enter the chroma format indicator ChromaFormatIdc for the image, as described in entry 7.3.

[0428] - When nnpfc_auxiliary_inp_idc equals 1, the filter strength control value array StrengthControlVal[idx] must contain real numbers in the range of 0 to 1 (inclusive) for the input image with index idx ranging from 0 to numInputPics - 1 (inclusive).

[0429] The input image at index 0 is the image in CandInputPicList that corresponds to the image activated by the NNPFA SEI message for the NNPF defined by the NNPFC SEI message. Input images with indices ranging from 1 to numInputPics - 1 (inclusive) precede the input image at index i - 1 in the output order.

[0430] Note 2 - The images in the CandInputPicList corresponding to the image are either the cropped decoded output image of that image or a filtered version of the cropped decoded output image of the previously applied PPF.

[0431] The variables SubWidthC and SubHeightC are derived from ChromaFormatIdc, as specified in Table 2.

[0432] Note 3 - More than one NNPFC SEI message can exist for the same image. When more than one NNPFC SEI message with different values ​​of nnpfc_id exists or is activated for the same image, they can have the same or different nnpfc_purpose values ​​and the same or different nnpfc_mode_idc values. ...

[0434] `nnpfc_absent_input_pic_zero_flag` equal to 1 indicates that NNPF expects the input image corresponding to an image that does not exist in the bitstream to be represented by an array of samples with sample values ​​equal to 0. `nnpfc_absent_input_pic_zero_flag` equal to 0 indicates that the input image `inputPicA` corresponding to an image that NNPF expects to not exist in the bitstream is represented by the input image `inputPicB`, which is the closest to `inputPicA` in the output order and whose corresponding image exists in the bitstream. ...

[0436] The sub-entry 8.28.3.2 has been modified as follows:

[0437] 8.28.2.3 Activating SEI message semantics using neural network post-processing filters ...

[0439] `nnpfa_no_prev_clvs_flag` equal to 1 indicates that the input image for NNPF does not originate from a previous CLVS. `nnpfa_no_prev_clvs_flag` equal to 0 indicates that the input image for NNPF may or may not originate from a previous CLVS.

[0440] Note 4 - The value of nnpfa_no_prev_clvs_flag can change from 0 to 1 when the current CLVS is spliced ​​from another bitstream adjacent to the previous CLVS, and the NNPFA SEI message will cause one or more input pictures to be selected, which have corresponding pictures from one or more previous CLVS, and thus may have a negative impact on the output of the target NNPF.

[0441] The value of nnpfa_no_foll_clvs_flag equal to 1 indicates that when the NNPFA SEI message persists for the last PU of the CLVS in output order, the NNPFA SEI message is treated as if it persisted for the last PU of the current layer within the bitstream in output order. When the NNPFA SEI message does not persist for the last PU of the CLVS in output order, or when nnpfa_no_foll_clvs_flag equals 0, the value of nnpfa_no_foll_clvs_flag has no specific effect.

[0442] Note 5 - When subsequent CLVSs are concatenated from different bitstreams adjacent to the current CLVS, the value of nnpfa_no_foll_clvs_flag can change from 0 to 1 for image rate upsampling NNPF. Therefore, the NNPF process interpolates the image to the end of the current CLVS using only the input image corresponding to the image from the current CLVS. ...

[0444] 6.2.2. H.266 / VVC Specification

[0445] Note that the H.266 / VVC specification below is based on the Joint Video Experts Group (JVET)-AG2027-v1 (publicly available here: https: / / www.jvet-experts.org / doc_end_user / documents / 33_Teleconference / wg11 / JVET-AG2027-v1.zip). The entries and sub-entries mentioned below are shown below. Entries and sub-entries not mentioned below are the same as those in JVET-AG2027-v1.

[0446] Replace sub-entry D.11.11 with the following:

[0447] D.11.11 Use of Post-processing Filter SEI Messages, including Neural Network Post-processing Filter Feature SEI Messages and Neural Network Post-processing Filter Activation SEI Messages.

[0448] Post-processing filters (PPFs) can be indicated by SEI messages that specify post-processing operations and whose payloadType values ​​are included in the list SeiProcessingOrderSeiList, which is defined in the semantics of the SPO SEI message.

[0449] Let currPic be the cropped decoded output image. For this cropped decoded output image, activate the PPF defined by the Neural Network Post-Processing Filter Feature (NNPFC) SEI message through, for example, the Neural Network Post-Processing Filter (NNPF), and let currLayerId be the nuh_layer_id value of currPic.

[0450] The list `candInputPicList` contains a list of images ordered by output, from which you select the input image for the PPF.

[0451] Note 1 - This list is updated each time a PPF is applied to the current image, through the PPF filtering process, unless that PPF is the last PPF applied to the current image.

[0452] When the PPF is not an NNPF, the PPF is considered to have only one input image, which is the image in candInputPicList corresponding to the current image.

[0453] Note 2 - The image corresponding to the cropped decoded output image in candInputPicList is either the cropped decoded output image itself or a filtered version of the cropped decoded output image that was previously used as the output image of the PPF.

[0454] If the PPF is the first PPF applied to the current image, then the following applies:

[0455] - CroppedWidth is set to equal to pps_pic_width_in_luma_samples for currPic - SubWidthC The value of ‌(pps_conf_win_left_offset + pps_conf_win_right_offset).

[0456] - CroppedHeight is set to equal to pps_pic_height_in_luma_samples for currPic - SubHeightC The value of (pps_conf_win_top_offset + pps_conf_win_bottom_offset).

[0457] - BitDepth Y and BitDepth C All of them are set to equal BitDepth.

[0458] - ChromaFormatIdc is set to equal sps_chroma_format_idc.

[0459] Otherwise (if the PPF is not the first PPF applied to the current image), the following applies:

[0460] - CroppedWidth is set to equal the width of the image in candInputPicList corresponding to the current image, in luminance samples.

[0461] - CroppedHeight is set to equal to the height of the image in candInputPicList corresponding to the current image, in units of luminance samples.

[0462] - BitDepthY is set to be equal to the bit depth BitDepthY of the luminance sample array of the image corresponding to the current image in candInputPicList.

[0463] - BitDepthC is set to equal to the bit depth BitDepthC of the chroma sample array (if any) of the image corresponding to the current image in candInputPicList.

[0464] - ChromaFormatIdc is set to be equal to the chroma format indicator ChromaFormatIdc of the image corresponding to the current image in candInputPicList.

[0465] The remainder of this entry applies when the PPF is an NNPF.

[0466] The requirement for bitstream consistency is that when a picture unit contains an NNPFA SEI message, the value of ph_pic_output_flag in the picture header contained in that picture unit must be equal to 1.

[0467] Note 3 - Since only the cropped decoded output image is used as the input image for NNPF when NNPF is the first PPF applied to currPic, the value of ph_pic_output_flag in the image header of the encoded / decoded image corresponding to each input image of NNPF is equal to 1.

[0468] The variable pictureRateUpsamplingFlag is set to equal to ( ( nnpfc_purpose & 0x08 ) >0 ) ? 1 : 0.

[0469] The variable numInputPics is set to equal nnpfc_num_input_pics_minus1 + 1.

[0470] The variable numInferences is derived as follows:

[0471] - If all of the following conditions are true, then the variable numPostRoll is set to the value of i that makes nnpfc_interpolated_pics[i] greater than 0, and the variable numInferences is set to 1 + numPostRoll:

[0472] - nnpfc_purpose equals 8 (i.e., the sole purpose of NNPF is image rate upsampling).

[0473] - nnpfa_persistence_flag equals 1.

[0474] - Only for a single i value greater than 0, nnpfc_interpolated_pics[i] is greater than 0.

[0475] - Any of the following conditions is true:

[0476] - currPic is the last picture in the output order of the bitstream with nuh_layer_id equal to currLayerId.

[0477] - currPic is the last image in the CLVS in the output order, and nnpfa_no_foll_clvs_flag is equal to 1.

[0478] - Otherwise, if all of the following conditions are true, the variable numPostRoll is set to equal InpIdx[i], where the value of i makes nnpfa_output_flag[i] equal to 1, and the variable numInferences is set to equal 1 + numPostRoll:

[0479] - pictureRateUpsamplingFlag equals 0.

[0480] - numInputPics is greater than 1.

[0481] - nnpfa_persistence_flag equals 1.

[0482] - For a single idx value in the range of 0 to NumInpPicsInOutputTensor - 1 (inclusive), nnpfa_output_flag[idx] is equal to 1, and for that single idx value, InpIdx[idx] is greater than 0.

[0483] - Any of the following conditions is true:

[0484] - currPic is the last picture in the output order of the bitstream with nuh_layer_id equal to currLayerId.

[0485] - currPic is the last image in the CLVS in the output order, and nnpfa_no_foll_clvs_flag is equal to 1.

[0486] Otherwise, the variable numInferences is set to 1.

[0487] For each value of j in the range 0 to numInferences - 1 (inclusive), the following derivation applies to the input images of NNPF, such that each input image is an image in candInputPicList:

[0488] The arrays inputPic[i] and inputPresentFlag[i] (which represent all input images and the existence of input images, respectively) in the range of 0 to numInputPics - 1 (inclusive) are defined as follows:

[0489] - When j is greater than 0, for each k value in the range of 0 to j - 1 (inclusive), inputPic[k] is set to the image in candInputPicList corresponding to currPic, and inputPresentFlag[k] is set to equal to 0.

[0490] - The j-th input image inputPic[j] is set to the image corresponding to currPic in candInputPicList, and inputPresentFlag[j] is set to 1.

[0491] - When numInputPics is greater than 1, for each value of i in the range from j + 1 to numInputPics - 1 (inclusive), sorted in ascending order of i, the following applies:

[0492] - If both of the following conditions are true, then inputPic[i] is set to the image corresponding to prevPic in candInputPicList, and inputPresentFlag[i] is set to 1:

[0493] - Any of the following conditions is true:

[0494] - pictureRateUpsamplingFlag equals 1, and currPic is associated with a frame packing arrangement SEI message having a specific value of frame_packing_arrangement_type equal to 5 and fp_current_frame_is_frame0_flag, and there exists a cropped decoded output image prevPic, which is the last image in output order among all cropped decoded output images. All cropped decoded output images have a nuh_layer_id equal to currLayerId, are in output order before inputPic[i-1], and are associated with a frame packing arrangement SEI message having the same value of frame_packing_arrangement_type equal to 5 and fp_current_frame_is_frame0_flag.

[0495] - if pictureRateUpsamplingFlag is equal to 0 or currPic is not associated with a frame packing arrangement SEI message with frame_packing_arrangement_type equal to 5, and there exists a cropped decoded output image prevPic, which is the last image in output order among all cropped decoded output images, and all cropped decoded output images have nuh_layer_id equal to currLayerId and are before inputPic[i - 1] in output order.

[0496] - nnpfa_no_prev_clvs_flag equals 0 or the encoded / decoded image corresponding to prevPic and the current image exist in the same CLVS.

[0497] - Otherwise, the following applies:

[0498] - inputPic[i] is set to the same image as inputPic[i-1], and inputPresentFlag[i] is set to 0.

[0499] - The requirement for bitstream consistency is that when pictureRateUpsamplingFlag is equal to 1, nnpfc_interpolated_pics[i-1] must be equal to 0.

[0500] - The requirement for bitstream consistency is that when inputPresentFlag[i] equals 0 and nnpfc_input_pic_output_flag[i] equals 1, for the value of idx that makes InpIdx[idx] equal to i, the value of nnpfa_output_flag[idx] must be equal to 0.

[0501] - To interpret NNPFC SEI messages, the following variables are specified:

[0502] - For each value i in the range of 0 to numInputPics - 1 (inclusive), the luminance sample array CroppedYPic[i] and the chrominance sample arrays CroppedCbPic[i] and CroppedCrPic[i] (if they exist) are derived as follows:

[0503] - The variable sourcePic is derived as follows:

[0504] - If inputPresentFlag[i] equals 1 or nnpfc_absent_input_pic_zero_flag equals 0, then sourcePic is set to inputPic[i].

[0505] - Otherwise (inputPresentFlag[i] equals 0 and nnpfc_absent_input_pic_zero_flag equals 1), sourcePic is set to an image with a luminance sample array of CroppedWidth × CroppedHeight samples equal to 0 and a Cb and Cr sample array of (CroppedWidth / SubWidthC) × (CroppedHeight / SubHeightC) samples equal to 0.

[0506] - The luminance sample array CroppedYPic[i] and the chrominance sample arrays CroppedCbPic[i] and CroppedCrPic[i] (if present) are set as two-dimensional arrays of the decoded sample values ​​of the Y, Cb and Cr components of sourcePic, respectively.

[0507] - For all values ​​of i in the range from 0 to numInputPics - 1 (inclusive), the array StrengthControlVal[i] for the input image of NNPF is derived as follows:

[0508] - StrengthControlVal[i] is set to equal to (firstSliceQp) Y The value of (63 + QpBdOffset) ÷ (63 + QpBdOffset) is given by firstSliceQp. Y Equals the SliceQp of the first strip of the decoded output image after cropping corresponding to inputPic[i]. Y .

[0509] No more than two NNPFC SEI messages with the same nnpfc_id value should exist in a single picture unit. If two NNPFC SEI messages with the same nnpfc_id value exist in a picture unit, these SEI messages must have different content. If two NNPFC SEI messages with the same nnpfc_id but different content exist in the same picture unit, these two NNPFC SEI messages must be in the same SEI NAL unit.

[0510] 7. References

[0511] [1] ITU-T and ISO / IEC, “Efficient video coding and decoding”, Recommendation ITU-T H.265 | ISO / IEC23008-2 (current version).

[0512] [2] ITU-T and ISO / IEC, “Multifunctional video coding and decoding”, Recommendation ITU-T H.266 | ISO / IEC23090-3.

[0513] [3] ITU-T and ISO / IEC, “Multifunctional supplemental enhancement information messages for encoding and decoding video bitstreams”, ITU-T Recommendation H.274 | ISO / IEC 23002-7.

[0514] [4] S. McCarthy, M.M. Hannuksela and Y.-K. Wang (eds.), JVET-AE2027, “SEI processing order of SEI messages in VVC (draft 5)”.

[0515] [5] S. McCarthy, T. Chujoh, M. Hannuksela, GJ Sullivan and Y.-K. Wang (eds.), “Additional SEI messages to VSEI (draft 5)”, JVET output document JVET-AE2006, publicly available online: https: / / jvet-experts.org / doc_end_user / current_document.php?id=13271.

[0516] [6] B. Bross, E. François, MM Hannuksela, A. Tourapis and Y.-K. Wang (eds.), “New Levels of VVC and Additional Enhancements Related to Systems (Draft 6)”, JVET Output Document JVET-AE2005, publicly available online: https: / / jvet-experts.org / doc_end_user / current_document.php?id=13270.

[0517] Figure 1 This is a block diagram illustrating an example video processing system 4000 in which various techniques disclosed herein may be implemented. Various implementations may include some or all of the components of system 4000. System 4000 may include an input 4002 for receiving video content. The video content may be received in a raw or uncompressed format, such as 8 or 10-bit multi-component pixel values, or it may be in a compressed or encoded format. Input 4002 may represent a network interface, a peripheral bus interface, or a storage interface. Examples of network interfaces include wired interfaces (such as Ethernet, Passive Optical Networking (PON), etc.) and wireless interfaces (such as Wi-Fi or cellular interfaces).

[0518] System 4000 may include an encoding / decoding component 4004 capable of implementing the various encoding / decoding or coding methods described in this document. Encoding / decoding component 4004 can reduce the average bit rate from the video input 4002 to the output of encoding / decoding component 4004 to produce an encoded / decoded representation of the video. Encoding / decoding techniques are therefore sometimes referred to as video compression or video transcoding techniques. The output of encoding / decoding component 4004 may be stored or transmitted via a communication connection such as that represented by component 4006. The bitstream (or encoded / decoded) representation of the video received at input 4002, whether stored or communicated, may be used by component 4008 to generate pixel values ​​or displayable video to be transmitted to display interface 4010. The process of generating user-visible video from the bitstream representation is sometimes referred to as video decompression. Furthermore, although some video processing operations are referred to as “encoding / decoding” operations or tools, it should be understood that encoding / decoding tools or operations are used by the encoder, and the corresponding decoding tools or operations that inversely convert the encoding / decoding results will be performed by the decoder.

[0519] Examples of peripheral bus interfaces or display interfaces may include Universal Serial Bus (USB), High Definition Multimedia Interface (HDMI), or DisplayPort. Examples of storage interfaces include Serial Advanced Technology Attachment (SATA), Peripheral Component Interconnect (PCI), Integrated Drive Electronic Devices (IDE), etc. The technologies described in this document can be embodied in a variety of electronic devices, such as mobile phones, laptops, smartphones, or other devices capable of performing digital data processing and / or video display.

[0520] Figure 2 This is a block diagram of an example video processing apparatus 4100. Apparatus 4100 can be used to implement one or more methods described herein. Apparatus 4100 can be embodied in a smartphone, tablet, computer, Internet of Things (IoT) receiver, etc. Apparatus 4100 may include one or more processors 4102, one or more memories 4104, and video processing circuitry 4106. The processors(multiple) 4102 may be configured to implement one or more methods described herein. The memories(multiple) 4104 may be used to store data and code for implementing the methods and techniques described herein. The video processing circuitry 4106 may be used to implement some of the techniques described herein in hardware circuitry. In some embodiments, the video processing circuitry 4106 may be at least partially included in the processor 4102, such as a graphics coprocessor.

[0521] Figure 3This is a flowchart of an example method 4200 for video processing. In step 4202, method 4200 determines a post-processing filter (PPF), wherein a general post-processing filtering procedure using the PPF (including but not limited to NNPF) is specified. In step 4204, a conversion between visual media data and a bitstream is performed based on the PPF. The conversion may include encoding at the encoder, decoding at the decoder, or a combination thereof.

[0522] It should be noted that method 4200 can be implemented in a means of processing video data (such as a video encoder 4400, a video decoder 4500, and / or an encoder 4600) including a processor and a non-transitory memory having instructions thereon. In this case, the instructions cause the processor to execute method 4200 when executed by the processor. Furthermore, method 4200 can be executed by a non-transitory computer-readable medium including a computer program product for use by a video codec device. The computer program product includes computer-executable instructions stored on the non-transitory computer-readable medium, causing the video codec device to execute method 4200 when executed by a processor.

[0523] Figure 4 This is a block diagram illustrating an example video encoding / decoding system 4300 that can utilize the techniques disclosed herein. The video encoding / decoding system 4300 may include a source device 4310 and a destination device 4320. The source device 4310 generates encoded video data, and this source device 4310 may be referred to as a video encoding device. The destination device 4320 can decode the encoded video data generated by the source device 4310, and this destination device 4320 may be referred to as a video decoding device.

[0524] Source device 4310 may include video source 4312, video encoder 4314, and input / output (I / O) interface 4316. Video source 4312 may include sources such as video capture devices, interfaces for receiving video data from video content providers, and / or computer graphics systems for generating video data, or combinations of such sources. Video data may include one or more pictures. Video encoder 4314 encodes the video data from video source 4312 to generate a bitstream. The bitstream may include a sequence of bits forming a codec representation of the video data. The bitstream may include codec pictures and associated data. Codec pictures are codec representations of pictures. Associated data may include sequence parameter sets, picture parameter sets, and other syntax structures. I / O interface 4316 may include a modulator / demodulator (modem) and / or transmitter. Encoded video data may be transmitted directly to destination device 4320 via network 4330 through I / O interface 4316. Encoded video data may also be stored on storage medium / server 4340 for access by destination device 4320.

[0525] The destination device 4320 may include an I / O interface 4326, a video decoder 4324, and a display device 4322. The I / O interface 4326 may include a receiver and / or a modem. The I / O interface 4326 may acquire encoded video data from the source device 4310 or the storage medium / server 4340. The video decoder 4324 may decode the encoded video data. The display device 4322 may display the decoded video data to a user. The display device 4322 may be integrated with the destination device 4320 or may be external to the destination device 4320, wherein the destination device 4320 may be configured to interface with an external display device.

[0526] The video encoder 4314 and the video decoder 4324 can operate according to video compression standards, such as the High Efficiency Video Codec (HEVC) standard, the Multi-Functional Video Codec (VVC) standard, and other existing and / or further standards.

[0527] Figure 5 This is a block diagram illustrating an example of a video encoder 4400, which can be... Figure 4 The system 4300 shown includes a video encoder 4314. The video encoder 4400 can be configured to perform any or all of the techniques disclosed herein. The video encoder 4400 includes multiple functional components. The techniques described in this disclosure can be shared among the various components of the video encoder 4400. In some examples, a processor can be configured to perform any or all of the techniques described in this disclosure.

[0528] The functional components of the video encoder 4400 may include a segmentation unit 4401, a prediction unit 4402 (which may include a mode selection unit 4403, a motion estimation unit 4404, a motion compensation unit 4405, and an intra-frame prediction unit 4406), a residual generation unit 4407, a transform processing unit 4408, a quantization unit 4409, an inverse quantization unit 4410, an inverse transform unit 4411, a reconstruction unit 4412, a buffer 4413, and an entropy coding unit 4414.

[0529] In other examples, the video encoder 4400 may include more, fewer, or different functional components. In one example, the prediction unit 4402 may include an intra-block copy (IBC) unit. The IBC unit can perform prediction in an IBC mode, where at least one reference picture is the picture in which the current video block is located.

[0530] Furthermore, some components such as the motion estimation unit 4404 and the motion compensation unit 4405 can be highly integrated, but for illustrative purposes, they are shown separately in the example of the video encoder 4400.

[0531] The segmentation unit 4401 can segment an image into one or more video blocks. The video encoder 4400 and the video decoder 4500 can support various video block sizes.

[0532] The mode selection unit 4403 can select one of several encoding / decoding modes (intra-frame encoding / decoding or inter-frame encoding / decoding), for example, based on error results, and provide the resulting intra-frame or inter-frame encoded / decoded block to the residual generation unit 4407 to generate residual block data, and to the reconstruction unit 4412 to reconstruct the coded block for use as a reference image. In some examples, the mode selection unit 4403 can select an intra-frame / inter-frame joint prediction (CIIP) mode, where prediction is based on inter-frame prediction signals and intra-frame prediction signals. In the case of inter-frame prediction, the mode selection unit 4403 can also select a resolution for the block based on motion vectors (e.g., sub-pixel precision or integer pixel precision).

[0533] To perform inter-frame prediction on the current video block, motion estimation unit 4404 can generate motion information for the current video block by comparing one or more reference frames from buffer 4413 with the current video block. Motion compensation unit 4405 can determine the predicted video block for the current video block based on the motion information and decoded samples of images from buffer 4413 other than the image associated with the current video block.

[0534] The motion estimation unit 4404 and the motion compensation unit 4405 can perform different operations on the current video block, for example, depending on whether the current video block is in an I-band, P-band, or B-band.

[0535] In some examples, motion estimation unit 4404 can perform unidirectional prediction on the current video block, and can search for a reference video block for the current video block in the reference images of list 0 or list 1. Motion estimation unit 4404 can then generate a reference index indicating the reference image in list 0 or list 1 (which contains the reference video block) and a motion vector indicating the spatial displacement between the current video block and the reference video block. Motion estimation unit 4404 can output the reference index, prediction direction indicator, and motion vector as motion information for the current video block. Motion compensation unit 4405 can generate a predicted video block for the current block based on the reference video block indicated by the motion information of the current video block.

[0536] In other examples, motion estimation unit 4404 can perform bidirectional prediction on the current video block. Motion estimation unit 4404 can search for a reference video block for the current video block in the reference images in list 0, and can also search for another reference video block for the current video block in the reference images in list 1. Motion estimation unit 4404 can then generate reference indices indicating the reference images containing the reference video blocks in lists 0 and 1, and motion vectors indicating the spatial displacement between the reference video blocks and the current video block. Motion estimation unit 4404 can output the reference index and motion vector of the current video block as motion information for the current video block. Motion compensation unit 4405 can generate a predicted video block for the current video block based on the reference video blocks indicated by the motion information of the current video block.

[0537] In some examples, the motion estimation unit 4404 can output a complete set of motion information for use in the decoder's decoding process. In some examples, the motion estimation unit 4404 may not output a complete set of motion information for the current video. Instead, the motion estimation unit 4404 can reference the motion information of another video block to transmit the motion information of the current video block via a signal. For example, the motion estimation unit 4404 may determine that the motion information of the current video block is sufficiently similar to the motion information of neighboring video blocks.

[0538] In one example, the motion estimation unit 4404 may indicate a value to the video decoder 4500 in the syntax structure associated with the current video block, which indicates that the current video block has the same motion information as another video block.

[0539] In another example, motion estimation unit 4404 may identify another video block and motion vector difference (MVD) in the syntax structure associated with the current video block. The motion vector difference indicates the difference between the motion vector of the current video block and the motion vector of the indicated video block. Video decoder 4500 may use the motion vector of the indicated video block and the motion vector difference to determine the motion vector of the current video block.

[0540] As discussed above, the video encoder 4400 can transmit motion vectors via signaling in a predictive manner. Two examples of predictive signaling techniques that can be implemented by the video encoder 4400 include Advanced Motion Vector Prediction (AMVP) and Merge Pattern Signaling.

[0541] Intra-prediction unit 4406 can perform intra-prediction on the current video block. When intra-prediction unit 4406 performs intra-prediction on the current video block, it can generate prediction data for the current video block based on decoded samples from other video blocks in the same frame. The prediction data for the current video block can include the predicted video block and various syntax elements.

[0542] The residual generation unit 4407 can generate residual data for the current video block by subtracting (or more) predicted video blocks from the current video block. The residual data for the current video block may include residual video blocks corresponding to different sample components of the samples in the current video block.

[0543] In other examples, such as in skip mode, there may be no residual data for the current video block, and the residual generation unit 4407 may not perform subtraction operations.

[0544] The transform processing unit 4408 can generate one or more transform coefficient video blocks for the current video block by applying one or more transforms to the residual video blocks associated with the current video block.

[0545] After the transform processing unit 4408 generates a transform coefficient video block associated with the current video block, the quantization unit 4409 can 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.

[0546] The inverse quantization unit 4410 and the inverse transform unit 4411 can apply inverse quantization and inverse transform to the transform coefficient video block respectively to reconstruct the residual video block from the transform coefficient video block. The reconstruction unit 4412 can add the reconstructed residual video block to the corresponding samples of one or more predicted video blocks generated by the prediction unit 4402 to generate a reconstructed video block associated with the current block and store it in the buffer 4413.

[0547] After the video block is reconstructed by reconstruction unit 4412, a loop filtering operation can be performed to reduce video block artifacts in the video block.

[0548] Entropy encoding unit 4414 can receive data from other functional components of video encoder 4400. When entropy encoding unit 4414 receives data, it can perform one or more entropy encoding operations to generate entropy-encoded data and output a bitstream including the entropy-encoded data.

[0549] Figure 6 This is a block diagram illustrating an example of a video decoder 4500, which can be... Figure 4 The system 4300 shown includes a video decoder 4324. The video decoder 4500 can be configured to perform any or all of the techniques disclosed herein. In the example shown, the video decoder 4500 includes multiple functional components. The techniques described in this disclosure can be shared among the various components of the video decoder 4500. In some examples, a processor can be configured to perform any or all of the techniques described in this disclosure.

[0550] In the example shown, the video decoder 4500 includes an entropy decoding unit 4501, a motion compensation unit 4502, an intra-frame prediction unit 4503, an inverse quantization unit 4504, an inverse transform unit 4505, a reconstruction unit 4506, and a buffer 4507. In some examples, the video decoder 4500 can perform a decoding process that is generally contrasted with the encoding process described with respect to the video encoder 4400.

[0551] The entropy decoding unit 4501 can retrieve the encoded bitstream. The encoded bitstream may include entropy-encoded video data (e.g., encoded video data blocks). The entropy decoding unit 4501 can decode the entropy-encoded video data, and the motion compensation unit 4502 can determine motion information from the entropy-decoded video data, including motion vectors, motion vector precision, reference image list index, and other motion information. The motion compensation unit 4502 can determine this information, for example, by executing AMVP and Merge modes.

[0552] The motion compensation unit 4502 can generate motion compensation blocks and can perform interpolation based on an interpolation filter. The identifier of the interpolation filter to be used with sub-pixel accuracy can be included in the syntax element.

[0553] The motion compensation unit 4502 can use the interpolation filter used by the video encoder 4400 during the encoding of a video block to calculate the interpolation for sub-integer pixels of the reference block. The motion compensation unit 4502 can determine the interpolation filter used by the video encoder 4400 based on the received syntax information, and the motion compensation unit 4502 can use the interpolation filter to generate a prediction block.

[0554] The motion compensation unit 4502 may use some syntax information to determine the size of the blocks used to encode (multiple) frames and / or (multiple) stripes of the encoded video sequence, segmentation information describing how each macroblock of the image of the encoded video sequence is segmented, a mode indicating how each segment is encoded, one or more reference frames (and a list of reference frames) for each inter-frame codec block, and other information for decoding the encoded video sequence.

[0555] Intra-prediction unit 4503 can use, for example, an intra-prediction mode received in the bitstream to form prediction blocks from spatially adjacent blocks. Inverse quantization unit 4504 inverse quantizes (i.e., dequantizes) the quantized video block coefficients provided in the bitstream and decoded by entropy decoding unit 4501. Inverse transform unit 4505 applies the inverse transform.

[0556] The reconstruction unit 4506 can sum the residual block with the corresponding predicted block generated by the motion compensation unit 4502 or the intra-frame prediction unit 4503 to form a decoded block. If necessary, a deblocking filter can also be used to filter the decoded block to eliminate block artifacts. The decoded video block is then stored in a buffer 4507, which provides a reference block for subsequent motion compensation / intra-frame prediction and also generates decoded video for presentation on a display device.

[0557] Figure 7 This is a schematic diagram of an example encoder 4600. Encoder 4600 is suitable for implementing VVC techniques. Encoder 4600 includes three loop filters: a deblocking filter (DF) 4602, a sample adaptive compensation (SAO) 4604, and an adaptive loop filter (ALF) 4606. Unlike DF 4602, which uses predefined filters, SAO 4604 and ALF 4606 utilize the original samples of the current image, respectively, by adding compensation and by applying a finite impulse response (FIR) filter, and by utilizing the encoded / decoded side information through signal transmission compensation and filter coefficients to reduce the mean square error between the original and reconstructed samples. ALF 4606 is located in the last processing stage of each image and can be thought of as a tool to attempt to capture and repair artifacts caused by previous stages.

[0558] The encoder 4600 also includes an intra-frame prediction component 4608 and a motion estimation / compensation (ME / MC) component 4610 configured to receive input video. The intra-frame prediction component 4608 is configured to perform intra-frame prediction, while the ME / MC component 4610 is configured to perform inter-frame prediction using a reference image obtained from a reference image buffer 4612. Residual blocks from inter-frame or intra-frame prediction are fed into a transform (T) component 4614 and a quantization (Q) component 4616 to generate quantized residual transform coefficients, which are then fed into an entropy encoding / decoding component 4618. The entropy encoding / decoding component 4618 entropy-encodes and decodes the prediction results and quantized transform coefficients and transmits them to a video decoder (not shown). The quantization component output from the quantization component 4616 can be fed into an inverse quantization (IQ) component 4620, an inverse transform component 4622, and a reconstruction (REC) component 4624. REC component 4624 is able to output images to DF 4602, SAO 4604 and ALF 4606 for filtering before these images are stored in reference image buffer 4612.

[0559] Figure 8This is a flowchart of an example method 4700 for video processing. In step 4702, method 4700 determines to apply a selected processing chain to the image, wherein the selected processing chain includes applying one or more post-processing filters (PPFs) to the image. In step 4704, a conversion between visual media data and a bitstream is performed based on the PPFs. The conversion may include encoding at the encoder, decoding at the decoder, or a combination thereof.

[0560] It should be noted that method 4700 can be implemented in a means for processing video data (such as a video encoder 4400, a video decoder 4500, and / or an encoder 4600) including a processor and a non-transitory memory having instructions thereon. In this case, the instructions cause the processor to execute method 4700 when executed by the processor. Furthermore, method 4700 can be executed by a non-transitory computer-readable medium including a computer program product for use by a video codec device. The computer program product includes computer-executable instructions stored on the non-transitory computer-readable medium, causing the video codec device to execute method 4700 when executed by a processor.

[0561] The following provides a list of preferred solutions as examples.

[0562] The following solutions illustrate examples of the techniques discussed in this article.

[0563] 1. A method for processing media data, comprising: determining a post-processing filter (PPF), wherein a general post-processing filtering procedure is specified using the PPF, including but not limited to the NNPF; and performing a conversion between visual media data and a bitstream based on the PPF.

[0564] 2. The method according to Solution 1, wherein PPFs are grouped and the PPF groups are interchangeable, such that only one PPF group can be selected for application to any given image.

[0565] 3. The method according to any one of solutions 1-2, wherein the PPFs within the selected PPF group are applied in a cascade manner, such that the output of one PPF is used as the input of the next PPF to be applied.

[0566] 4. The method according to any one of solutions 1-3, wherein, regardless of how many PPFs are applied to the current image in the selected PPF group, and regardless of what type of PPFs they are, an image output by an earlier applied PPF is allowed to be used as an image input by a later applied PPF.

[0567] 5. The method according to any one of solutions 1-4, wherein a list CandInputPicList including all candidates for the input image is initialized or reset to contain a list of cropped decoded images generated from the decoding BitstreamToFilter in output order for each current image before the first PPF is applied to the current image, and CandInputPicList is updated each time a PPF is applied, possibly except for the PPF last applied to the current image.

[0568] 6. The method according to any one of solutions 1-5, wherein after applying PPF to the current image, the list CandInputPicList is updated by replacing each of the images in the list that have PPF output images with the corresponding PPF output image.

[0569] 7. The method according to any one of solutions 1-6, wherein, before applying PPF to the current image, the list CandInputPicList is updated by replacing each image in the list that has a corresponding PPF output image and is in the order of output preceding the current image with the corresponding PPF output image.

[0570] 8. The method according to any one of solutions 1-7, wherein after applying PPF to the current image, the list CandInputPicList is updated by inserting the interpolated image (if any) into the list and placing the interpolated image such that all images in the updated list are arranged in the output order.

[0571] 9. The method according to any one of solutions 1-8, wherein after applying PPF to the current image, the list CandInputPicList is updated by: replacing each image in the list of images with corresponding PPF output images with corresponding PPF output images, and inserting interpolated images (if any) into the list, and placing the interpolated images such that all images in the updated list are arranged in output order.

[0572] 10. The method according to any one of solutions 1-9, wherein the output of the general post-processing filtering procedure is specified as a list of output images, ListOutputPics, which may include multiple images output by the last applied PPF.

[0573] 11. The method according to any one of solutions 1-10, wherein the list ListOutputPics may include cropped decoded images that do not have corresponding output images with PPF output by any applied PPF, or wherein the list ListOutputPics may include PPF output images that are PPF output by a PPF that is not the last applied PPF when a particular image is the current image.

[0574] 12. The method according to any one of solutions 1-11, wherein before applying any PPF, a list ListOutputPics is initialized to contain a list of cropped decoded images generated from the decoder BitstreamToFilter in output order, and the list ListOutputPics is updated each time a PPF is applied.

[0575] 13. The method according to any one of solutions 1-12, wherein after the PPF is applied, the list ListOutputPics is updated by replacing each image in the list of images with the corresponding PPF output image with the corresponding PPF output image.

[0576] 14. The method according to any one of solutions 1-13, wherein after the PPF is applied, the list ListOutputPics is updated by inserting interpolated images (if any) into the list and placing the interpolated images such that all images in the updated list are arranged in output order.

[0577] 15. The method according to any one of solutions 1-14, wherein after the PPF is applied, the list ListOutputPics is updated by: replacing each image in the list of images with the corresponding PPF output image with the corresponding PPF output image, and inserting the interpolated image (if any) into the list and placing the interpolated image such that all images in the updated list are arranged in output order.

[0578] 16. An apparatus for processing video data, comprising: a processor; and a non-transitory memory having instructions thereon, wherein the instructions, when executed by the processor, cause the processor to perform the method according to any one of solutions 1-15.

[0579] 17. A non-transitory computer-readable medium comprising a computer program product for use by a video codec apparatus, the computer program product comprising computer-executable instructions stored on the non-transitory computer-readable medium such that, when executed by a processor, the video codec apparatus performs the method according to any one of solutions 1-15.

[0580] 18. A non-transitory computer-readable recording medium for storing a bitstream of video generated by a method performed by a video processing apparatus, wherein the method comprises: determining a post-processing filter (PPF), wherein a general post-processing filtering procedure using a PPF including but not limited to an NNPF is specified; and generating a bitstream based on the determination.

[0581] 19. A method for storing a bitstream of video, comprising: determining a post-processing filter (PPF), wherein a general post-processing filtering procedure is specified using a PPF including but not limited to an NNPF; generating a bitstream based on the determination; and storing the bitstream in a non-transitory computer-readable recording medium.

[0582] 20. A method, apparatus or system described in this document.

[0583] The following solutions illustrate further examples of the techniques discussed in this article.

[0584] 1. A method for processing media data, comprising: determining a processing chain of post-processing filters (PPFs) to be applied to visual media data by: obtaining a list of cropped decoded images arranged in output order; selecting a processing chain; applying each PPF in the processing chain to each cropped decoded image in the list; and replacing the cropped decoded images in the list with the processed images; and performing a conversion between the visual media data and a bitstream based on the processing chain.

[0585] 2. The method according to Solution 1, wherein, regardless of how many PPFs are applied to the current image in the selected processing chain, and regardless of the type of PPFs in the selected processing chain, it is permissible to use the output image of an earlier applied PPF as the input image of a later applied PPF.

[0586] 3. The method according to any one of solutions 1-2, wherein the list of cropped decoded images is obtained as a result of the decoded bitstream.

[0587] 4. The method according to any one of solutions 1-3, wherein when an image in the list is replaced, the image's attributes are also updated as part of the list, and the updated attributes include: image width in luminance samples, image height in luminance samples, bit depth of the luminance sample array for the image, bit depth of the chroma sample array for the image, chroma format indicator for the image, or a combination thereof.

[0588] 5. The method according to any one of solutions 1-4, wherein when an image is inserted into the list, the image's attributes are also updated as part of the list, and the updated attributes include: image width in luminance samples, image height in luminance samples, bit depth of the luminance sample array for the image, bit depth of the chroma sample array for the image, chroma format indicator for the image, or a combination thereof.

[0589] 6. The method according to any one of solutions 1-5, wherein the list of cropped decoded images arranged in output order is generated for each current image decoded bitstream before the first PPF is applied to the current image, and the list is updated each time a PPF is applied to the current image except for the last PPF applied to the current image.

[0590] 7. The method according to any one of solutions 1-6, wherein after applying PPF to the current image, the list is updated by replacing each image in the list with the corresponding PPF output image.

[0591] 8. The method according to any one of solutions 1-7, wherein, before applying PPF to the current image, the list is updated by replacing each image in the list that has a corresponding PPF output image with the corresponding PPF output image in the output order preceding the current image.

[0592] 9. The method according to any one of solutions 1-8, wherein after applying PPF to the current image, the list is updated by inserting the interpolated image (if any) into the list and placing the interpolated image so that all images in the updated list are arranged in the output order.

[0593] 10. The method according to any one of solutions 1-9, wherein after applying a PPF to the current image, the list is updated by replacing each image in the list with a corresponding PPF output image, and inserting an interpolated image (if any) into the list and placing the interpolated image so that all images in the updated list are arranged in the output order.

[0594] 11. The method according to any one of solutions 1-10, wherein after applying PPF, the list is updated by: 1) replacing each image in the list of images with the corresponding PPF output image with the corresponding PPF output image, and 2) inserting interpolated or extrapolated images (if any) into the list and placing the interpolated or extrapolated images so that all images in the updated list are arranged in output order.

[0595] 12. The method described in solutions 1-11, wherein the list is a list of candidate input images (CandInputPicList).

[0596] 13. The method according to any one of solutions 1-12, wherein the conversion includes encoding visual media data into a bitstream.

[0597] 14. The method according to any one of solutions 1-12, wherein the conversion includes decoding visual media data from a bitstream.

[0598] 15. A non-transitory computer-readable recording medium storing a bitstream of video generated by a method performed by a video processing apparatus, wherein the method comprises: determining a processing chain of post-processing filters (PPFs) to be applied to visual media data by: obtaining a list of cropped decoded images arranged in output order; selecting a processing chain; applying each PPF in the processing chain to each cropped decoded image in the list; and replacing the cropped decoded images in the list with the processed images; and generating a bitstream based on the determination.

[0599] 16. The non-transitory computer-readable recording medium according to Solution 15, wherein the list of cropped decoded images is obtained as a result of the decoded bitstream.

[0600] 17. A non-transitory computer-readable recording medium according to any one of solutions 15-16, wherein, after applying a PPF, the list is updated by: 1) replacing each image in the list of images with a corresponding PPF output image with a corresponding PPF output image, and 2) inserting interpolated or extrapolated images (if any) into the list and placing the interpolated or extrapolated images such that all images in the updated list are arranged in output order.

[0601] 18. A method for storing a bitstream of video, comprising: determining a processing chain of post-processing filters (PPFs) to be applied to visual media data by: obtaining a list of cropped decoded images arranged in output order; selecting a processing chain; applying each PPF in the processing chain to each cropped decoded image in the list; and replacing the cropped decoded images in the list with the processed images; generating a bitstream based on the determination; and storing the bitstream in a non-transitory computer-readable recording medium.

[0602] 19. The method according to solution 18, wherein the list of cropped decoded images is obtained as a result of the decoded bitstream.

[0603] 20. The method according to any one of solutions 18-19, wherein after applying PPF, the list is updated by: 1) replacing each image in the list of images with the corresponding PPF output image with the corresponding PPF output image, and 2) inserting interpolated or extrapolated images (if any) into the list and placing the interpolated or extrapolated images such that all images in the updated list are arranged in the output order.

[0604] 21. An apparatus for processing video data, comprising: a processor; and a non-transitory memory having instructions thereon, wherein the instructions, when executed by the processor, cause the processor to perform the method according to any one of solutions 1-14.

[0605] 22. A non-transitory computer-readable medium comprising a computer program product for use by a video codec device, the computer program product including computer-executable instructions stored on the non-transitory computer-readable medium such that, when the instructions are executed by a processor, the video codec device performs the method according to any one of solutions 1-14.

[0606] In the described solution, the encoder conforms to the format rules by generating a codec representation based on those rules. In the described solution, the decoder parses the syntax elements in the codec representation using known information about their presence or absence, based on the format rules, to produce the decoded video.

[0607] In this document, the term "video processing" can refer to video encoding, video decoding, video compression, or video decompression. For example, a video compression algorithm can be applied during the conversion from the pixel representation of a video to its corresponding bitstream representation, and vice versa. For example, the bitstream representation of the current video block can correspond to bits at the same position in the bitstream defined by the syntax, or bits propagated at different positions. For example, a macroblock can be encoded based on the error residual value after transformation and encoding / decoding, and also using bits from the header and other fields in the bitstream. Furthermore, during the conversion, the decoder can, based on this determination, parse the bitstream knowing whether certain fields may or may not be present, as described in the solutions above. Similarly, the encoder can determine whether to include or exclude specific syntax fields and generate the codec representation accordingly by including or excluding syntax fields from the codec representation.

[0608] The disclosed and other solutions, examples, embodiments, modules, and functional operations described in this document can be implemented in digital electronic circuits, or in computer software, firmware, or hardware, including the structures disclosed in this document and their structural equivalents, or in a combination of one or more. The disclosed and other embodiments can be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a computer-readable medium for execution by or control of the operation of a data processing apparatus. The computer-readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a material composition affecting machine-readable propagation signals, or a combination thereof. The term "data processing apparatus" includes all means, devices, and machines for processing data, including, for example, a programmable processor, a computer, or multiple processors or computers. In addition to hardware, the apparatus may also include code that creates an execution environment for an associated computer program, such as code constituting processor firmware, a protocol stack, a database management system, an operating system, or a combination thereof. Propagation signals are artificially generated signals, such as machine-generated electrical signals, optical signals, or electromagnetic signals, which are generated to encode information to be transmitted to a suitable receiver device.

[0609] Computer programs (also known as programs, software, software applications, scripts, or code) can be written in any programming language, including compiled or interpreted languages, and can be deployed in any form, including standalone programs or modules, components, subroutines, or other units suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the related program, or in multiple co-located files (e.g., a file storing one or more modules, subroutines, or code portions). A computer program can be deployed to execute on one computer or on multiple computers located at a single site or distributed across multiple sites and interconnected by a communications network.

[0610] The processing and logic flows described in this document can be executed by one or more programmable processors that execute one or more computer programs to perform functions by manipulating input data and generating outputs. The processing and logic flows can also be executed by special-purpose logic circuitry, and the devices can be implemented as special-purpose logic circuitry, such as FPGAs (Field-Programmable Gate Arrays) or ASICs (Application-Specific Integrated Circuits).

[0611] Processors suitable for executing computer programs include, for example, general-purpose and special-purpose microprocessors, and any one or more processors of any type of digital computer. Typically, a processor receives instructions and data from read-only memory or random access memory, or both. The basic components of a computer are a processor that executes instructions and one or more storage devices that store the instructions and data. Typically, a computer will also include one or more mass storage devices for storing data, such as magnetic disks, magneto-optical disks, or optical disks, or receive data from or transfer data to one or more mass storage devices via operative coupling, or both. However, a computer does not necessarily have such devices. Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and storage devices, including, for example, semiconductor storage devices such as EPROM, EEPROM, and flash memory devices; magnetic disks, such as internal hard disks or removable hard disks; magneto-optical disks; and CD-ROMs and DVD-ROMs. Processors and memory may be supplemented by or incorporated into special-purpose logic circuitry.

[0612] While this patent document contains numerous details, these details should not be construed as limiting any subject matter or the scope of the claims, but rather as descriptions of features specific to particular embodiments of a particular technology. In this patent document, certain features described in the context of individual embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented separately in multiple embodiments, or in any suitable sub-combination. Furthermore, although features may function in certain combinations as described above, and even were originally claimed in this manner, in some cases one or more features in the claimed combination may be removed from that combination, and the claimed combination may be for sub-combinations or variations thereof.

[0613] Similarly, although operations are depicted in a specific order in the accompanying drawings, this should not be construed as requiring such operations to be performed sequentially in the specific order or sequence shown, or requiring all shown operations to be performed in order to achieve the desired result. Furthermore, the division of various system components in the embodiments described in this patent document should not be construed as requiring such division in all embodiments.

[0614] Only a few implementations and examples are described, and other implementations, improvements and variations can be made based on what is described and shown in this patent document.

[0615] When there is no intermediate component (other than a line, trace, or other medium between the first and second components), the first component is directly coupled to the second component. When there is an intermediate component between the first and second components other than a line, trace, or other medium, the first component is indirectly coupled to the second component. The term "coupled" and its variations include direct coupling and indirect coupling. The use of the term "about" means including a range of ±10% of the following figures, unless otherwise specified.

[0616] While several embodiments have been provided in this disclosure, it should be understood that the disclosed systems and methods may be embodied in many other specific forms without departing from the spirit or scope of this disclosure. The present examples are intended to be illustrative rather than restrictive and are not intended to be limited to the details set forth herein. For example, various elements or components may be combined or integrated into another system, or certain features may be omitted or not implemented.

[0617] Furthermore, the technologies, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, technologies, or methods without departing from the scope of this disclosure. Other items shown or discussed as couplings may be directly connected or indirectly coupled or communicated through some interface, device, or intermediate component (whether electrical, mechanical, or otherwise). Those skilled in the art can identify examples of other changes, substitutions, and modifications, which may be made without departing from the spirit and scope of this disclosure.

Claims

1. A method for processing media data, comprising: The processing chain for applying post-processing filters (PPFs) to visual media data is determined by: obtaining a list of cropped decoded images arranged in output order; selecting the processing chain; applying each PPF in the processing chain to each cropped decoded image in the list; and replacing the cropped decoded images in the list with processed images. as well as The conversion between the visual media data and the bitstream is performed based on the processing chain.

2. The method as described in claim 1, wherein, Regardless of how many PPFs are applied to the current image in the selected processing chain, and regardless of the type of PPFs in the selected processing chain, it is permissible to use the output image of an earlier applied PPF as the input image of a later applied PPF.

3. The method according to any one of claims 1-2, wherein, The list of cropped decoded images is obtained as a result of decoding the bitstream.

4. The method according to any one of claims 1-3, wherein, When an image in the list is replaced, the image's attributes are also updated as part of the list, and the updated attributes include: image width in luminance samples, image height in luminance samples, bit depth of the luminance sample array for the image, bit depth of the chroma sample array for the image, chroma format indicator for the image, or a combination thereof.

5. The method according to any one of claims 1-4, wherein, When an image is inserted into the list, the image's attributes are also updated as part of the list, and the updated attributes include: image width in luminance samples, image height in luminance samples, bit depth of the luminance sample array for the image, bit depth of the chroma sample array for the image, chroma format indicator for the image, or a combination thereof.

6. The method according to any one of claims 1-5, wherein, The list of cropped decoded images, arranged in the output order, is generated for each current image before the first PPF is applied to the current image, and the list is updated each time a PPF is applied to the current image, except for the last PPF applied to the current image.

7. The method according to any one of claims 1-6, wherein, After applying a PPF to the current image, the list is updated by replacing each image in the list with the corresponding PPF output image.

8. The method according to any one of claims 1-7, wherein, Before applying a PPF to the current image, the list is updated by replacing each image in the list that has the corresponding PPF output image with the corresponding PPF output image, in the order of the output.

9. The method according to any one of claims 1-8, wherein, After applying PPF to the current image, the list is updated by inserting the interpolated image (if any) into the list and placing the interpolated image so that all images in the updated list are arranged in the output order.

10. The method according to any one of claims 1-9, wherein, After applying a PPF to the current image, the list is updated by replacing each image in the list with the corresponding PPF output image, and inserting interpolated images (if any) into the list and placing the interpolated images so that all images in the updated list are arranged in the output order.

11. The method according to any one of claims 1-10, wherein, After applying the PPF, the list is updated in the following ways: 1) each image in the list that has the corresponding PPF output image is replaced with the corresponding PPF output image, and 2) interpolated or extrapolated images (if any) are inserted into the list and the interpolated or extrapolated images are placed so that all images in the updated list are arranged in the output order.

12. The method as described in claims 1-11, wherein, The list is a list of candidate input images (CandInputPicList).

13. The method according to any one of claims 1-12, wherein, The conversion includes encoding the visual media data into the bitstream.

14. The method according to any one of claims 1-12, wherein, The conversion includes decoding the visual media data from the bitstream.

15. A non-transitory computer-readable recording medium storing a bitstream of video generated by a method performed by a video processing apparatus, wherein, The method includes: The processing chain for applying post-processing filters (PPFs) to visual media data is determined by: obtaining a list of cropped decoded images arranged in output order; selecting the processing chain; applying each PPF in the processing chain to each cropped decoded image in the list; and replacing the cropped decoded images in the list with processed images; and Based on the determination, a bit stream is generated.

16. The non-transitory computer-readable recording medium of claim 15, wherein, The list of cropped decoded images is obtained as a result of decoding the bitstream.

17. The non-transitory computer-readable recording medium as described in any one of claims 15-16, wherein, After applying the PPF, the list is updated in the following ways: 1) each image in the list that has the corresponding PPF output image is replaced with the corresponding PPF output image, and 2) interpolated or extrapolated images (if any) are inserted into the list and the interpolated or extrapolated images are placed so that all images in the updated list are arranged in the output order.

18. A method for storing a bitstream of video, comprising: The processing chain for applying post-processing filters (PPFs) to visual media data is determined by: obtaining a list of cropped decoded images arranged in output order; selecting the processing chain; applying each PPF in the processing chain to each cropped decoded image in the list; and replacing the cropped decoded images in the list with processed images. Based on the determination, a bit stream is generated; as well as The bit stream is stored in a non-transitory computer-readable recording medium.

19. The method of claim 18, wherein, The list of cropped decoded images is obtained as a result of decoding the bitstream.

20. The method of any one of claims 18-19, wherein, After applying the PPF, the list is updated in the following ways: 1) each image in the list that has the corresponding PPF output image is replaced with the corresponding PPF output image, and 2) interpolated or extrapolated images (if any) are inserted into the list and the interpolated or extrapolated images are placed so that all images in the updated list are arranged in the output order.

21. An apparatus for processing video data, comprising: processor; and a non-transitory memory thereon having instructions, wherein the instructions, when executed by the processor, cause the processor to perform the method as described in any one of claims 1-14.

22. A non-transitory computer-readable medium comprising a computer program product for use by a video codec apparatus, the computer program product comprising computer-executable instructions stored on the non-transitory computer-readable medium such that, when executed by a processor, the computer-executable instructions cause the video codec apparatus to perform the method as described in any one of claims 1-14.

Images