WO2026006403A1 - Signalling of the enhancer neural network in a generative video stream - Google Patents

Abstract

A mechanism for processing video data is disclosed. The mechanism includes determining a generative face video (GFV) supplemental enhancement information (SEI) message comprises a GFV matrix element integer value at matrix position m,k of a jth matrix with an ith matrix type (gfv_matrix_element_int[ i ][ j ][ k ][ m ]), where the gfv_matrix_element_int[ i ][ j ][ k ][ m ] shall be in the range of 0 to 2³² − 2, inclusive. The mechanism further includes performing a conversion between a visual media data and a bitstream based on the GFV SEI message.

Description

Signalling Of The Enhancer Neural Network In A Generative Video Stream CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims the priority to and benefits of U.S. Provisional Patent Application No. 63/664,940, filed on June 27, 2024. All the aforementioned patent applications are hereby incorporated by reference in their entireties. TECHNICAL FIELD [0002] This patent document relates to generation, storage, and consumption of digital audio video media information in a file format. BACKGROUND [0003] Digital video accounts for the largest bandwidth used on the Internet and other digital communication networks. As the number of connected user devices capable of receiving and displaying video increases, the bandwidth demand for digital video usage is likely to continue to grow. SUMMARY [0004] A first aspect relates to a method for processing video data comprising: determining a generative face video (GFV) supplemental enhancement information (SEI) message comprises a GFV matrix element integer value at matrix position m,k of a jth matrix with an ith matrix type (gfv_matrix_element_int[ i ][ j ][ k ][ m ]), where the gfv_matrix_element_int[ i ][ j ][ k ][ m ] shall be in the range of 0 to 232 − 2, inclusive; and performing a conversion between a visual media data and a bitstream based on the GFV SEI message. [0005] A second aspect relates to an apparatus for processing video data comprising: a processor; and a non- transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to perform any of the preceding aspects. [0006] A third aspect relates to non-transitory computer readable medium comprising a computer program product for use by a video coding device, the computer program product comprising computer executable instructions stored on the non-transitory computer readable medium such that when executed by a processor cause the video coding device to perform the method of any of the preceding aspects. [0007] A fourth aspect relates to a non-transitory computer-readable recording medium storing a bitstream of a video which is generated by a method performed by a video processing apparatus, wherein the method comprises: determining a generative face video (GFV) supplemental enhancement information (SEI) message comprises a GFV matrix element integer value at matrix position m,k of a jth matrix with an ith matrix type (gfv_matrix_element_int[ i ][ j ][ k ][ m ]), where the gfv_matrix_element_int[ i ][ j ][ k ][ m ] shall be in the range of 0 to 232 − 2, inclusive; and generating a bitstream based on the determining. [0008] A fifth aspect relates to a method for storing bitstream of a video comprising: determining a generative face video (GFV) supplemental enhancement information (SEI) message comprises a GFV matrix element integer value at matrix position m,k of a jth matrix with an ith matrix type (gfv_matrix_element_int[ i ][ j ][ k ][ m ]), where the gfv_matrix_element_int[ i ][ j ][ k ][ m ] shall be in the range of 0 to 232 − 2, inclusive; generating a bitstream based on the determining; and storing the bitstream in a non-transitory computer-readable recording medium. [0009] For the purpose of clarity, any one of the foregoing embodiments may be combined with any one or more of the other foregoing embodiments to create a new embodiment within the scope of the present disclosure. [0010] These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims. BRIEF DESCRIPTION OF THE DRAWINGS [0011] For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts. [0012] FIG.1 is a schematic block diagram of an example of generative face video compression. [0013] FIG.2 is a block diagram showing an example video processing system. [0014] FIG.3 is a block diagram of an example video processing apparatus. [0015] FIG.4 is a flowchart for an example method of video processing. [0016] FIG.5 is a block diagram that illustrates an example video coding system. [0017] FIG.6 is a block diagram that illustrates an example encoder. [0018] FIG.7 is a block diagram that illustrates an example decoder. [0019] FIG.8 is a schematic diagram of an example encoder. [0020] FIG.9 is a flowchart for an example method of video processing. DETAILED DESCRIPTION [0021] It should be understood at the outset that although an illustrative implementation of one or more embodiments are provided below, the disclosed systems and/or methods may be implemented using any number of techniques, whether currently known or yet to be developed. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated below, including the exemplary designs and implementations illustrated and described herein, but may be modified within the scope of the appended claims along with their full scope of equivalents. [0022] Section headings are used in the present document for ease of understanding and do not limit the applicability of techniques and embodiments disclosed in each section only to that section. Furthermore, H.266 terminology is used in some description only for ease of understanding and not for limiting scope of the disclosed techniques. As such, the techniques described herein are applicable to other video codec protocols and designs also. In the present document, editing changes are shown to text by bold italics indicating cancelled text and bold indicating added text, with respect to the Versatile Video Coding (VVC) specification and/or the supplemental enhancement information (SEI) messages for coded video bitstreams (VSEI) standard. 1. Initial discussion [0023] This disclosure is related to signalling of the translator and generator neural networks (NNs) in a generative video system. Specifically, it is related to signalling of the enhancer neural network, e.g., denoted as EnhancerNN( ), in the context of the design of a generative face video enhancement (GFVE) supplemental enhancement information (SEI) message, as well as specifying the value ranges for some syntax elements in generative face video (GFV) or GFVE SEI message. The ideas may be applied individually or in various combinations, for video bitstreams coded by any codec, e.g., the versatile video coding (VVC) standard and/or the versatile SEI messages for coded video bitstreams (VSEI) standard, and may also be applied in generative video systems other than a generative face video system. The ideas may be applied individually or in various combinations, for image and/or video coding methods and specifications. 2. Abbreviations [0024] The following abbreviations may be referred to throughout this disclosure: [0025] Adaptation Parameter Set (APS), Access Unit (AU), Coded Layer Video Sequence (CLVS), Coded Layer Video Sequence Start (CLVSS), Cyclic Redundancy Check (CRC), Coded Video Sequence (CVS), Finite Impulse Response (FIR), Intra Random Access Point (IRAP), Network Abstraction Layer (NAL), Neural-Network Post-Processing Filter (NNPF), Neural-Network Post-Filter Activation (NNPFA), Neural-Network Post-Filter Characteristics (NNPFC), Picture Parameter Set (PPS), Picture Unit (PU), Random Access Skipped Leading (RASL), Supplemental Enhancement Information (SEI), Step-wise Temporal Sublayer Access (STSA), Uniform Resource Identifier (URI), Video Coding Layer (VCL), Versatile Supplemental Enhancement Information, also referred to as Rec. ITU-T H.274 | ISO/IEC 23002-7 (VSEI), Video Usability Information (VUI), Versatile Video Coding, also referred to as Rec. ITU-T H.266 | ISO/IEC 23090-3 (VVC). 3. Further discussion 3.1. Video Coding Standards [0026] Video coding standards have evolved primarily through the development of the well-known International Telecommunication Union (ITU) telecommunication standardization sector (ITU-T) and International Organization for Standardization (ISO) / International Electrotechnical Commission (IEC) standards. The ITU-T produced H.261 and H.263, ISO/IEC produced Moving Picture Experts Group (MPEG)-1 and MPEG- 4 Visual, and the two organizations jointly produced the H.262/MPEG-2 Video and H.264/MPEG-4 Advanced Video Coding (AVC) and H.265/HEVC [1] standards. Since H.262, the video coding standards are based on the hybrid video coding structure wherein temporal prediction plus transform coding are utilized. The Versatile Video Coding (VVC) standard (ITU-T H.266 | ISO/IEC 23090-3) [2] and the associated Versatile Supplemental Enhancement Information for coded video bitstreams (VSEI) standard (ITU-T H.274 | ISO/IEC 23002-7) [3] have been designed for use in a maximally broad range of applications, including both the traditional uses such as television broadcast, video conferencing, or playback from storage media, and also newer and more advanced use cases such as adaptive bit rate streaming, video region extraction, composition and merging of content from multiple coded video bitstreams, multiview video, scalable layered coding, and viewport-adaptive 360° immersive media. 3.2. SEI messages in general and in VVC and VSEI [0027] SEI messages assist in processes related to decoding, display or other purposes. However, SEI messages are not required for constructing the luma or chroma samples by the decoding process. Conforming decoders are not required to process this information for output order conformance. Some SEI messages are required for checking bitstream conformance and for output timing decoder conformance. Other SEI messages are not required for check bitstream conformance. [0028] Annex D of VVC specifies syntax and semantics for SEI message payloads for some SEI messages, and specifies the use of the SEI messages and VUI parameters for which the syntax and semantics are specified in ITU-T H.274 | ISO/IEC 23002-7. 3.3. Generative face video SEI message [0029] FIG.1 is a schematic block diagram of an example of generative face video compression 100. In the scheme, some base pictures or called key pictures are coded using a conventional video codec, e.g. VVC, and subsequent pictures include meta data of face features, e.g. head position, eye matrix representing the open-close status and level of eyes. A decoder uses a generative neural network to form a decoded video based on those key pictures and subsequent face feature data. [0030] Joint Video Experts Team (JVET)-AH2032 [4] includes the specification of the generative face video SEI message, as follows. 8.36.1 Generative face video SEI message syntax generative_face_video ( payloadSize ) { Descriptor gfv_nn_uri st(v) } if( gfv_coordinate_z_present_flag ) { gfv_coordinate_dz_abs[ i ] u(v) for( m = 0; m <matrixWidth[ i ]; m++ ) { if( !gfv_matrix_pred_flag ) { 8.36.2 Generative face video SEI message semantics [0031] The generative face video (GFV) SEI message indicates facial parameters and specifies a facial parameter translator network, denoted as TranslatorNN( ), that may be used to convert various formats of facial parameters signaled in the SEI message into a fixed format of parameters, and a face picture generator neural network, denoted as GenerativeNN( ), that may be used to generate output pictures using the fixed format of facial parameters and previously decoded output pictures. [0032] NOTE 1 – Facial parameters could be determined from source pictures prior to encoding. Such source pictures may be referred to as driving pictures. [0033] NOTE 2 – Previously decoded output pictures input to GenerativeNN( ) may be a base picture (a decoded output picture that provides the reference texture from which the face pictures may be generated) and, optionally, a picture that can be fused by GenerativeNN( ) to improve background texture and facial details. When the current picture is not a base picture, the GFV SEI message may be used to generate a face picture based on the previously decoded base picture, the facial parameters conveyed by the GFV SEI message, and, optionally, the current decoded picture for fusion purpose. [0034] Use of this SEI message requires the definition of the following variables: – Input and output picture width and height in units of luma samples, denoted herein by CroppedWidth and CroppedHeight, respectively. – Luma sample array baseCroppedYPic and chroma sample arrays baseCroppedCbPic and baseCroppedCrPic for a decoded output picture, denoted as BasePicture, corresponding to a source base picture. – Luma sample array driveCroppedYPic and chroma sample arrays driveCroppedCbPic and driveCroppedCrPic for a decoded output picture, denoted as DrivePicture, corresponding to a source driving picture. – Bit depth BitDepthY for the luma sample array of the input and output pictures. – Bit depth BitDepthC for the chroma sample arrays, if any, of the input and output pictures. – A chroma format indicator, denoted herein by ChromaFormatIdc, as described in subclause 7.3. [0035] The variables SubWidthC and SubHeightC are derived from ChromaFormatIdc. [0036] gfv_id contains an identifying number that may be used to identify face feature information and specify a neural network that may be used as TranslatorNN( ). The value of gfv_id shall be in the range of 0 to 2³²– − 2, inclusive. Values of gfv_id from 256 to 511, inclusive, and from 2³¹ to 2³²–− 2, inclusive, are reserved for future use by ITU-T | ISO/IEC. Decoders conforming to this edition of this document encountering a GFV SEI ^{message with gfv_id in the range of 256 to 511, inclusive, or in the range of 231 to 232–− 2, inclusive, shall ignore} the SEI message. [0037] gfv_cnt specifies a GFV SEI message instance count value for this gfv_id value within a picture unit. [0038] The gfv_cnt of the first GFV SEI message, in decoding order, with a particular value of gfv_id within picture unit shall be equal to 0. When gfv_cnt assigned to currGfvCnt is greater than 0, a GFV SEI message with the same gfv_id value and gfv_cnt equal to currGfvCnt − 1 shall precede the current GFV SEI message in decoding order in the same picture unit. [0039] The value of gfv_cnt shall be in the range of 0 to 65535, inclusive. [0040] gfv_base_pic_flag equal to 1 indicates the current decoded output picture corresponds to a base picture. gfv_base_pic_flag equal to 0 indicates the current decoded output picture does not correspond to a base picture or this SEI message does not specify syntax elements for a base picture. When gfv_base_pic_flag is not present, it is inferred to be equal to 0. [0041] The following constraints apply to the value of gfv_base_pic_flag: – When a GFV SEI message is the first GFV SEI message, in decoding order, that has a particular gfv_id value within the current CLVS, the value of gfv_base_pic_flag shall be equal to 1. – When a GFV SEI message that has a particular gfv_id value has gfv_base_pic_flag being equal to 0, this SEI message pertains to the current decoded picture and all subsequent decoded pictures of the current layer, in output order, until the end of the current CLVS or up to but excluding the decoded picture that follows the current decoded picture in output order within the current CLVS and is associated with a subsequent GFV SEI message, in decoding order, having gfv_base_pic_flag equal to 0 and that particular gfv_id value within the current CLVS, whichever is earlier. [0042] This annex specifies the codestream structure (sub-clause 11.2) and entropy decoder operations. Encoder shall produce stream compliant to the specified order of elements. [0043] gfv_nn_present_flag equal to 1 indicates a neural network that may be used as a TranslatorNN( ) is contained or indicated by the SEI message. gfv_nn_present_flag equal to 0 indicates a neural network that may be used as a TranslatorNN( ) is not contained or indicated by the SEI message. When gfv_nn_present_flag is not present, it is inferred to be 0. [0044] When a GFV SEI message with a particular value of gfv_id is present in an IRAP picture unit or in a picture unit that follows an IRAP picture unit in output order and is not preceded in output order by any picture unit that follows the IRAP picture in output order and has a GFV SEI message with that particular value of gfv_id, gfv_nn_present_flag shall be present and equal to 1. [0045] When gfv_nn_present_flag is equal to 0 and TranslatorNN is referenced in the semantics of this SEI message, the applicable TranslatorNN is defined by the GFV SEI message that is present in the last preceding picture unit in output order that has that has the same value of gfv_id as that in the current GFV SEI message and gfv_nn_present_flag equal to 1. [0046] gfv_nn_base_flag, gfv_nn_mode_idc, gfv_nn_reserved_zero_bit_a, gfv_nn_tag_uri, gfv_nn_uri, gfv_nn_payload_byte[ i ] specify a neural network that may be used as a TranslatorNN( ). gfv_nn_base_flag, gfv_nn_mode_idc, gfv_nn_reserved_zero_bit_a, gfv_nn_tag_uri, gfv_nn_uri, gfv_nn_payload_byte[ i ] have the same syntax and semantics as nnpfc_base_flag, nnpfc_mode_idc, nnpfc_reserved_zero_bit_a, nnpfc_tag_uri, nnpfc_uri, nnpfc_payload_byte[ i ], respectively. [0047] When either of the following conditions is true, GFV SEI messages shall have the same SEI payload content: – The GFV SEI messages are present in the same picture unit, have gfv_cnt equal to 0, have gfv_nn_base_flag present, and have the same value of gfv_id and gfv_nn_base_flag, – The GFV SEI messages are present in the same picture unit, have the same value of gfv_cnt that is greater than 0, and have the same value of gfv_id. [0048] gfv_drive_pic_fusion_flag, when present, equal to 1 indicates the current decoded picture, which corresponds to a driving picture that may be used for fusion, may be input to GenerativeNN( ). gfv_drive_pic_fusion_flag equal to 0 indicates the current decoded picture should not be input to GenerativeNN( ). [0049] NOTE 3 – A gfv_drive_pic_fusion_flag value of 1 can be used, for example, to indicate that the current decoded picture can be used to improve face details or handle background changes. [0050] NOTE 4 – Fusion takes the three inputs: the base picture, features from keypoints and/or matrices carried in the GFV SEI message, and the current decoded picture, and outputs a picture. [0051] NOTE 5 – When current decoded picture corresponds to a driving picture, it should be marked as not for output purpose. [0052] gfv_low_confidence_face_parameter_flag equal to 1 indicates the facial parameters have been derived with low confidence. gfv_low_confidence_face_parameter_flag equal to 0 indicates the confidence information of the facial parameters is not specified. [0053] gfv_coordinate_present_flag equal to 1 indicates that coordinate information of keypoints is present. gfv_coordinate_present_flag equal to 0 indicates that coordinate information of keypoints is not present. [0054] It is a requirement of bitstream conformance that when gfv_matrix_type_idx[ i ] for any i from 0 to gfv_num_matrix_types_minus1 is equal to 0 or 1, the value of gfv_coordinate_present_flag shall be equal to 1. [0055] gfv_coordinate_precision_factor_minus1 plus 1 indicates the length, in bits, of syntax elements gfv_coordinate_x_abs[i], gfv_coordinate_y_abs[i], gfv_coordinate_z_abs[i], gfv_coordinate_dx_abs[ i ], gfv_coordinate_dy_abs[ i ] and gfv_coordinate_dz_abs[ i ]. [0056] gfv_num_kps_minus1 plus 1 indicates the number of keypoints. The value of gfv_num_kp_minus1 shall be in the range of 0 to 2¹⁰ – 1, inclusive. [0057] gfv_kp_pred_flag equal to 1 indicates syntax elements gfv_coordinate_dx_abs[ i ] ,gfv_coordinate_dy_abs[ i ], and gfv_coordinate_dz_abs[ i ] are present and syntax elements gfv_coordinate_dx_sign_flag[ i ], gfv_coordinate_dy_sign_flag[ i ] and gfv_coordinate_dz_sign_flag[ i ] may be present. gfv_kp_pred_flag equal to 0 indicates gfv_coordinate_x_abs[ i ] ,gfv_coordinate_y_abs[ i ], and gfv_coordinate_z_abs[ i ] are present and syntax elements gfv_coordinate_x_sign_flag[ i ], gfv_coordinate_y_sign_flag[ i ] and gfv_coordinate_z_sign_flag[ i ] may be present. [0058] gfv_coordinate_z_present_flag equal to 1 indicates that z-axis coordinate information of the keypoints is present. coordinate_z_present_flag equal to 0 indicates that the z-axis coordinate information of the keypoints is not present. [0059] gfv_coordinate_z_max_value_minus1 plus 1 indicates the maximum absolute value of z-axis coordinates of keypoints. [0060] gfv_coordinate_x_abs[ i ] is used to derive the x-axis coordinate of the i-th keypoint. [0061] gfv_coordinate_x_sign_flag[ i ] specifies the sign of the x-axis coordinate of the i-th keypoint. When gfv_coordinate_x_sign_flag[ i ] is not present, it is inferred to be equal to 0. [0062] gfv_coordinate_y_abs[ i ] is used to derive y-axis coordinate of i-th keypoint. [0063] gfv_coordinate_y_sign_flag[ i ] specifies the sign of the y-axis coordinate of the i-th keypoint. When gfv_coordinate_y_sign_flag[i] is not present, it is inferred to be equal to 0. [0064] gfv_coordinate_z_abs[ i ] is used to derive z-axis coordinate of the i-th keypoint. [0065] gfv_coordinate_z_sign_flag[ i ] specifies the sign of the z-axis coordinate of the i-th key point. When gfv_coordinate_z_sign_flag[ i ] is not present, it is inferred to be equal to 0. [0066] gfv_coordinate_dx_abs[ i ] specifies a difference value that is used to derive x-axis coordinate of the i-th keypoint. [0067] gfv_coordinate_dx_sign_flag[ i ] specifies the sign of the difference value of the x-axis coordinate of the i-th keypoint. When gfv_coordinate_dx_sign_flag[ i ] is not present, it is inferred to be equal to 0. [0068] gfv_coordinate_dy_abs[ i ] specifies a difference value that is used to derive y-axis coordinate of the i-th keypoint. [0069] gfv_coordinate_dy_sign_flag[ i ] specifies the sign of the difference value of the y-axis coordinate of the i-th keypoint. When gfv_coordinate_yd_sign_flag[i] is not present, it is inferred to be equal to 0. [0070] gfv_coordinate_dz_abs[ i ] specifies a difference value that is used to derive z-axis coordinate of the i-th keypoint. [0071] gfv_coordinate_dz_sign_flag[ i ] specifies the sign of the difference value of the z-axis coordinate of the i-th key point. When gfv_coordinate_dz_sign_flag[ i ] is not present, it is inferred to be equal to 0. [0072] The variables coordinateDeltaX[ i ], coordinateDeltaY[ i ] and coordinateDeltaZ[ i ] indicating the delta x-axis coordinate, delta y-axis coordinate and delta z-axis coordinate of the i-th keypoint, respectively, are derived as follows: ^^^^ ∗ ^^^_^^^^^^^^^^_^^_^^^^_^^^^^ ^ ^^ ∗ ^^^_^^^^^^^^^^_^^_^^^^ ^ ^ ∗ ^^^^^^^^^^^^ coordinateDeltaX[ i ] = ^^^ ^^^^_^^^^^^^^^^_^^^^^^^^^_^^^^^^_ ^^!^^ "^^ ^^^^ ∗ ^^^_^^^^^^^^^^_^#_^^^^_^^^^^ ^ ^^ ∗ ^^^_^^^^^^^^^^_^#_^^^^ ^ ^ ∗ ^^^^^^^$^^^^^ coordinateDeltaY[i] = ^^^ ^^^^_^^^^^^^^^^_^^^^^^^^^_^^^^^^_ ^^!^^ "^^ if (gfv_coordinate_z_present_flag ) ^^^^ ∗ ^^^^^^^^^^_^%_^^^^_^^^^^ ^ ^^ ∗ ^^^_^^^^^^^^^^_^%_^^^^ ^ ^ ∗^^^^_^^^^^^^^^^_%_ ^^_^^^!^_ ^^!^^"^^ coordinateDeltaZ[i] = ^^^ ^^!^^ "^^ [0073] The variables coordinateX[ i ], coordinateY[ i ] and when gfv_coordinate_z_present_flag is equal to 1, coordinateZ[ i ] indicating the x-axis coordinate, y-axis coordinate and z-axis coordinate of the i-th keypoint, respectively, are derived as follows: When gfv_kp_pred_flag is equal to 0, ^^^^ ∗ ^^^_^^^^^^^^^^_^_^^^^_^^^^^ ^ ^^ ∗ ^^^_^^^^^^^^^^_^_^^^^ ^ ^ ∗ ^^^^^^^^^^^^ coordinateX[ i ] = ^^^ ^^^^_^^^^^^^^^^_^^^^^^^^^_^^^^^^_ ^^!^^ "^^ ^^^ ^^^^_^^^^^^^^^^_^^^^^^^^^_^^^^^^_ ^^!^^ "^^ if coordinateZ[i] = ^^^^ ∗ ^^^_^^^^^^^^^^_%_^^^^_^^^^^ ^ ^^ ∗ ^^^_^^^^^^^^^^_%_^^^^ ^ ^ ∗^^^^_^^^^^^^^^^_%_ ^^_^^^!^_ ^^!^^"^^ ^^^ ^^^^_^^^^^^^^^^_^^^^^^^^^_^^^^^^_ ^^!^^ "^^ if( gfv_base_pic_flag ) { coordinateX[ i ] = (( i > 0 ) ? coordinateX[ i - 1 ] : 0 ) + coordinateDeltaX[ i ] coordinateY[ i ] = (( i > 0 ) ? coordinateY[ i - 1 ] : 0 ) + coordinateDeltaY[ i ] if (gfv_coordinate_z_present_flag ) coordinateZ[ i ] = (( i > 0 ) ? coordinateZ[ i - 1 ] : 0 ) + coordinateDeltaZ[ i ] } else { coordinateX[ i ] = BaseKpCoordinateX[ i ] + coordinateDeltaX[ i ] coordinateY[ i ] = BaseKpCoordinateY[ i ] + coordinateDeltaY[ i ] if (gfv_coordinate_z_present_flag ) coordinateZ[ i ] = BaseKpCoordinateZ[ i ] + coordinateDeltaZ[ i ] } where BaseKpCoordinateX[ i ], BaseKpCoordinateY[ i ], BaseKpCoordinateZ[ i ] indicating the x-axis, y- axis and z-axis coordinates, respectively, of the i-th keypoint for the base picture are derived as follows: if( gfv_base_pic_flag ) { BaseKpCoordinateX[ i ] = coordinateX[ i ] BaseKpCoordinateY[ i ] = coordinateY[ i ] if (gfv_coordinate_z_present_flag ) BaseKpCoordinateZ[ i ] = coordinateZ[ i ] } [0074] gfv_matrix_present_flag equal to 1 indicates that matrix parameters are present. gfv_matrix_present_flag equal to 0 indicates that matrix parameters are not present. [0075] gfv_matrix_element_precision_factor_minus1 plus 1 indicates the length, in bits, of syntax elements gfv_matrix_element_dec[ i ][ j ][ k ][ m ] and gfv_matrix_delta_element_dec[ i ][ j ][ k ][ m ]. [0076] gfv_num_matrix_types_minus1 plus 1 indicates the number of matrix types signalled in the SEI message. The value of gfv_num_matrix_types_minus1 shall be in the range of 0 to 2⁶ – 1, inclusive. It is a requirement of bitstream conformance that when gfv_matrix_pred_flag is equal to 1 and gfv_base_pic_flag is equal to 0, the value of gfv_num_matrix_types_minus1 shall be equal to the value of gfv_num_matrix_types_minus1 in each of the preceding GFV SEI message in decoding order in the current CLVS which has the same gfv_id value as the gfv_id value in the current SEI and has gfv_base_pic_flag equal to 1. [0077] gfv_matrix_pred_flag equal to 1 indicates syntax elements gfv_matrix_element_int [ i ][ j ][ k ][ m ] , gfv_matrix_element_dec [ i ][ j ][ k ][ m ] are present and gfv_matrix_element_sign_flag [ i ][ j ][ k ][ m ] may be present. gfv_matrix_pred_flag equal to 0 indicates gfv_matrix_delta_element_int [ i ][ j ][ k ][ m ] , gfv_matrix_delta_element_dec [ i ][ j ][ k ][ m ] are present and syntax element gfv_matrix_delta_element_sign_flag [ i ][ j ][ k ][ m ] may be present. When gfv_matrix_pred_flag is not present, it is inferred to be 0. [0078] gfv_matrix_type_idx[ i ] indicates the index of the i-th matrix type as specified in Table 1. Table 1. Specification of gfv_matrix_type_idx Value Specification Affi t l ti t i ith th i f 2*2 * o- D ce nd ng [0079] NOTE 6. The undefined matrix type is used to represent the matrix type rather than affine translation matrix, covariance matrix, rotation matrix, translation matrix and compact feature matrix. It is may be used by the user to extend the matrix type. [0080] gfv_num_matrices_equal_to_num_kps_flag[ i ] equal to 1 indicates that the number of matrices of the i-th matrix type is equal to gfv_num_kps_minus1 + 1. gfv_num_matrices_equal_to_num_kps_flag[ i ] equal to 0 indicates the number of matrices of the i-th matrix type is not equal to gfv_num_kps_minus1 + 1. When not present gfv_num_matrices_equal_to_num_kps_flag[ i ] is inferred to be equal to 0. [0081] gfv_num_matrices_info[ i ] provides information to derive the number of the matrices of the i-th matrix type. [0082] gfv_matrix_width_minus1[ i ] plus 1 indicates the width of the matrix of the i-th matrix type. [0083] gfv_matrix_height_minus1[ i ] plus 1 indicates the height of the matrix of the i-th matrix type. [0084] gfv_matrix_for_3D_space_flag[ i ] equal to 1 indicates the matrix of the i-th matrix type is a matrix defined in three-dimensional space. gfv_matrix_for_3D_space_flag[ i ] equal to 0 indicates the matrix of the i-th matrix type is a matrix defined in two-dimensional space. [0085] When gfv_matrix_width_minus1[ i ] is not present, it is inferred as follows: – If gfv_matrix_type_idx[ i ] is equal to 0, 1 or 4, and one of coordinate_z_present_flag and gfv_matrix_for_3D_space_flag[ i ] is present and equal to 1, gfv_matrix_width_minus1[i] is inferred to be equal to 2 – otherwise, if matrix_type_idx[ i ] is equal to 0, 1 or 4, and one of coordinate_z_present_flag and gfv_matrix_for_3D_space_flag[ i ] is present and equal to 0, gfv_matrix_width_minus1[ i ] is inferred to be equal to 1 – otherwise (matrix_type_idx[ i ] is equal to 5 or 6), gfv_matrix_width_minus1[ i ] is inferred to be equal to 0 [0086] When gfv_matrix_height_minus1[ i ] is not present, it is inferred as follows: – If matrix_type_idx is equal to 0, 1, 4, 5 or 6, and one of gfv_coordinate_z_present_flag and gfv_matrix_for_3D_space_flag[ i ] is present and equal to 1, gfv_matrix_height_minus1[ i ] is inferred to be equal to 2. – otherwise (gfv_matrix_type_idx is equal to 0, 1, 4, 5 or 6, and one of gfv_coordinate_z_present_flag and gfv_matrix_for_3D_space_flag[ i ] is 0), gfv_matrix_height _minus1[ i ] is inferred to be equal to 1. [0087] The variables matrixWidth[ i ] and matrixHeight[ i ] indicating the width and height of the matrix of the i-th matrix type are derived as follows matrixWidth[ i ] = gfv_matrix_width_minus1[ i ] + 1 matrixHeight[ i ] = gfv_matrix_height_minus1[ i ] + 1 [0088] gfv_num_matrices_minus1[ i ] plus 1 indicates the number of matrices of the i-th matrix type. [0089] The variable numMatrices[ i ] indicating the number of the matrices of the i-th matrix type is derived as follows: if( gfv_matrix_type_idx[ i ] == 0 || gfv_matrix_type_idx[ i ] == 1 ) { if( gfv_coordinate_present_flag ) numMatrices[ i ] = gfv_num_matrices_equal_to_num_kps_flag[ i ] ? gfv_num_kps_minus1 + 1 : ( gfv_num_matrices_info[ i ] < gfv_num_kp_minus1 ? gfv_num_matrices_info [ i ] + 1 : gfv_num_matrices_info [ i ] + 2 ) else numMatrices[ i ] = gfv_num_matrices_info[ i ] + 1 } else if( gfv_matrix_type_idx[ i ] >= 2 && gfv_matrix_type_idx[ i ] < 7) numMatrices[ i ] = 1 else numMatrices[ i ] = gfv_num_matrices_minus1[ i ] + 1 [0090] It is a requirement of bitstream conformance that when gfv_matrix_pred_flag is equal to 1 and gfv_base_pic_flag is equal to 0, the values of numMatrices[ i ] , matrixWidth[ i ], and matrixHeight[ i ] for i in the range of 0 to gfv_num_matrix_types_minus1, inclusive shall be respectively equal to the values of numMatrices[ i ], matrixWidth[ i ], and matrixHeight[ i ] for i in the range of 0 to gfv_num_matrix_types_minus1, inclusive in each of the preceding GFV SEI message in decoding order in the current CLVS which has the same gfv_id value as the gfv_id value in the current SEI and has gfv_base_pic_flag equal to 1. [0091] gfv_matrix_element_int[ i ][ j ][ k ][ m ] indicates the integer part of the value of the matrix element at position (m, k) of the j-th matrix of the i-th matrix type. [0092] gfv_matrix_element_dec[ i ][ j ][ k ][ m ] indicates the decimal part of the value of the matrix element at position (m, k) of the j-th matrix of the i-th matrix type. [0093] gfv_matrix_element_sign_flag[ i ][ j ][ k ][ m ] indicates the sign of the matrix element at position (m, k) of the j-th matrix of the i-th matrix type. When gfv_matrix_element_sign_flag[ i ][ j ][ k ][ m ]is not present, it is inferred to be equal to 0. [0094] gfv_matrix_delta_element_int[ i ][ j ][ k ][ m ] indicates the integer part of the difference value of the matrix element at position (m, k) of the j-th matrix of the i-th matrix type. [0095] gfv_matrix_delta_element_dec[ i ][ j ][ k ][ m ] indicates the decimal part of the difference value of the matrix element at position (m, k) of the j-th matrix of the i-th matrix type. [0096] gfv_matrix_delta_element_sign_flag[ i ][ j ][ k ][ m ] indicates the sign of the difference value of the matrix element at position (m, k) of the j-th matrix of the i-th matrix type. When gfv_matrix_element_sign_flag[ i ][ j ][ k ][ m ]is not present, it is inferred to be equal to 0. [0097] The variable matrixElementDeltaVal[ i ][ j][ k ][ m ] representing the difference value of the matrix element at position (m, k) of the j-th matrix of the i-th matrix type is derived as follows: m_{atrixElementDeltaVal[ i][ j ][ k ][ m ] = ^1 ' 2 ∗ gfv_matrix_delta_element_sign_flag^ i ^^ j ^^ k ^^ m ^^ ∗} ement_int^ ^^^_ ^^^^^_^^^^^_^^^ ^^^_^^^^ ^ ^^ : ^^ ; ^^ ^ ^gfv_matrix_delta_el i ^^ j ^^ k ^^ m ^ 9 ^^^ ^^^^_ ^^^^^_^^^ ^^^_^^^^^^^^^_^^^^^^_ ^^!^^ "^^ ^ [0098] The variable matrixElementVal[ i ][ j][ k ][ m ] representing the value of the matrix element at position (m, k) of the j-th matrix of the i-th matrix type is derived as follows: When gfv_matrix_pred_flag is equal to 0: m_{atrixElementVal[ i][ j ][ k ][ m ] = ^1 ' 2 ∗ gfv_matrix_element_sign_flag^ i ^^ j ^^ k ^^ m ^^ ∗} ^^^_ ^^^^^_^^^ ^^^_^^^^ ^ ^^ : ^^ ; ^^ ^ ^gfv_matrix_element_int^{^} i ^{^^} j ^{^^} k ^{^^} m ^{^} 9 ^^^ ^^^^_ ^^^^^_^^^ ^^^_^^^^^^^^^_^^^^^^_ ^^!^^ "^^ ^ if( gfv_base_pic_flag ) BaseMatrixElementVal[ i][ j ][ k ][ m ] = matrixElementVal[ i][ j ][ k ][ m ] When gfv_matrix_pred_flag is equal to 1: matrixElementVal[ i][ j ][ k ][ m ] = BaseMatrixElementVal[ i][ j ][ k ][ m ] + matrixElementDeltaVal[ i][ j ][ k ][ m ] [0099] For a particular gfv_id value, the following process is used in increasing order of gfv_cnt to generate a video picture per each GFV SEI message that has gfv_base_pic_flag equal to 0 and a unique value of gfv_cnt within a picture unit: DeriveSigParam( ) TranslatorNN (sigKeyPoint , sigMatrix) DeriveInputTensors( ) if( gfv_base_pic_flag == 0 && gfv_drive_pic_fusion_flag == 0) { if(ChromaFormatIdc == 0 ) GenerativeNN( inputBaseY, inputBaseKeyPoint, inputBaseMatrix, inputDriveKeyPoint, inputDriveMatrix) else GenerativeNN( inputBaseY, inputBaseCb, inputBaseCr, inputBaseKeyPoint, inputBaseMatrix, inputDriveKeyPoint, inputDriveMatrix) } else if(gfv_base_pic_flag == 0 && gfv_drive_pic_fusion_flag == 1) { if(ChromaFormatIdc == 0 ) GenerativeNN( inputBaseY, inputDriveY, inputBaseKeyPoint, inputBaseMatrix, inputDriveKeyPoint, inputDriveMatrix) else GenerativeNN( inputBaseY, inputBaseCb, inputBaseCr, inputDriveY, inputDriveCb, inputDriveCr , inputBaseKeyPoint, inputBaseMatrix,, inputDriveKeyPoint, inputDriveMatrix) } StoreOutputTensors( ) [0100] The process DeriveSigParam () for deriving the inputs of TranslatorNN () is specified as follows: The keypoint coordinate array sigKeyPoint and the matrix sigMatrix are derived as follows: if( gfv_coordinate_present_flag ) { for ( i = 0; i< = gfv_num_kps_minus1; i++ ) { sigKeyPoint[ i ][ 0 ] = coordinateX[ i ] sigKeyPoint[ i ][ 1 ] = coordinateY[ i ] if ( gfv_coordinate_z_present_flag ) sigKeyPoint[ i ][ 2 ] = coordinateZ[ i ] } } else { for ( i = 0; i < =num_kps_minus1; i++ ) { sigKeyPoint [ i ][ 0 ] = 0 sigKeyPoint [ i ][ 1 ] = 0 if ( gfv_coordinate_z_present_flag ) sigKeyPoint [ i ][ 2 ] = 0 } } if( gfv_matrix_present_flag ) { for ( i = 0; i <= gfv_num_matrix_types_minus1; i++ ) { for ( j = 0; j < numMatrices[ i ]; j++ ) { for( k = 0; k < matrixHeight [ i ]; k++ ) { for ( l = 0;l < matrixWidth [ i ]; l++) { sigMatrix[ i ][ j ][ k ][ l ] = matrixElementVal[ i ][ j][ k][ l ] } } } } } else { for ( i = 0; i <= gfv_num_matrix_types_minus1; i++ ) { for ( j = 0; j < numMatrices[ i ]; j++ ) { for( k = 0; k < matrixHeight [ i ]; k++ ) { for ( l = 0;l < matrixWidth [ i ]; l++) { sigMatrix [ i ][ j ][ k ][ l ] = 0 } } } } } [0101] TranslatorNN( ) is a process to translate the various formats of the facial parameters carried in the SEI message to the fixed format of the facial parameters to be input to the generative network to generate the output picture. [0102] Inputs to TranslatorNN() are: – sigKeyPoint; and – sigMatrix [0103] Outputs of TranslatorNN() are: – convKeyPoint and convNumKeyPoint – convMatrix and convNumMatrix, convMatrixWidth, convMatrixHeight [0104] The process DeriveInputTensors( ) for deriving the inputs of GenerativeNN ( ) is specified as follows: When gfv_base_pic_flag is equal to 1, the BasePicture input tensor inputBaseY, inputBaseCb and inputBaseCr are derived as follows: for( x = 0; x < CroppedWidth; x++ ) { for ( y = 0; y < CroppedHeight; y++ ) { inputBaseY[ x ][ y ] = InpY( baseCroppedYPic[ x ][ y ] ) } } if (ChromaFormatIdc !=0) { for( x = 0; x < CroppedWidth/ SubWidthC; x++ ) { for ( y = 0; y < CroppedHeight/ SubHeightC; y++ ) { inputBaseCb[ x][ y ] = InpC( baseCroppedCbPic[ x][ y ] ) inputBaseCr[ x][ y ] = InpC( baseCroppedCrPic[ x ][ y ] ) } } } When gfv_drive_pic_fusion_flag is equal to 1, the DrivePicture luma sample array inputDriveY, inputDriveCb and input DriveCr are derived as follows: for( x = 0; x< CroppedWidth; x++ ) { for ( y = 0; y< CroppedHeight; y++ ) { inputDriveY[ x ][ y ] = InpY( driveCroppedYPic[ x ][ y ] ) } } if (ChromaFormatIdc !=0) { for( x = 0; x< CroppedWidth/ SubWidthC; x++ ) { for ( y = 0; y < CroppedHeight/ SubHeightC; y++ ) { InputDriveCb[ x][ y ] = InpC( driveCroppedCbPic[ x][ y ] ) InputDriveCr[ x][ y ] = InpC( driveCroppedCrPic[ x ][ y ] ) } } } When gfv_base_pic_flag is equal to 0, the keypoint coordinate array inputDriveKeyPoint and the matrix inputDriveMatrix for the current picture are derived as follows: for ( i = 0; i < = convNumKeyPoint; i++ ) { inputDriveKeyPoint[ i ][ 0 ] = convKeyPoint[ i ][ 0 ] inputDriveKeyPoint [ i ][ 1 ] = convKeyPoint[ i ][ 1 ] inputDriveKeyPoint [ i ][ 2 ] = convKeyPoint[ i ][ 2 ] } for( j = 0; j < convNumMatrix; j++ ) { for( k=0; k< convMatrixHeight; k++ ) { for ( m=0;m< convMatrixWidth; m++) { inputDriveMatrix[ j ][ k ][ m ] = convMatrix [ j ][ k ][ m ] } } } When gfv_base_pic_flag is equal to 1, the keypoint coordinate array inputBaseKeyPoint and the matrix inputBaseMatrix for the base picture are derived as follows: for ( i = 0; i < = convNumKeyPoint; i++ ) { inputBaseKeyPoint[ i ][ 0 ] = convKeyPoint[ i ][ 0 ] inputBaseKeyPoint [ i ][ 1 ] = convKeyPoint[ i ][ 1 ] inputBaseKeyPoint [ i ][ 2 ] = convKeyPoint[ i ][ 2 ] } for( j = 0; j < convNumMatrix; j++) { for( k=0; k< convMatrixHeight; k++ ) { for ( l=0;l< convMatrixWidth; l++) { inputBaseMatrix[ j ][ k ][ l ] = convMatrix [ j ][ k ][ l ] } } } [0105] Where the functions InpY( ) and InpC( ) are specified as follows: InpY( x ) = x ÷ ( ( 1 << BitDepth_Y ) – 1 ) x = x ÷ 1 << BitDepthC ) – 1 ) ( ) is a process to generate the sample values of an output picture corresponding to a when gfc_base_pic_flag is equal to 0. Input values to GenerativeNN( ) and output values from GenerativeNN( ) are real numbers. [0107] Inputs to GenerativeNN() are: – When gfv_base_pic_flag is equal to 0 and gfv_drive_pic_fusion_flag is equal to 0 and ChromaFormatIdc is equal to 0: inputBaseY, inputBaseKeyPoint, inputBaseMatrix, inputDriveKeyPoint, inputDriveMatrix – When gfv_base_pic_flag is equal to 0 and gfv_drive_pic_fusion_flag is equal to 0 and ChromaFormatIdc is not equal to 0: inputBaseY, inputBaseCb, inputBaseCr, inputBaseKeyPoint, inputBaseMatrix, inputDriveKeyPoint, inputDriveMatrix – When gfv_base_pic_flag is equal to 0 and gfv_drive_pic_fusion_flag is equal to 1 and ChromaFormatIdc is equal to 0: inputBaseY, inputDriveY, inputBaseKeyPoint, inputBaseMatrix, inputDriveKeyPoint, inputDriveMatrix – When gfv_base_pic_flag is equal to 0 and gfv_drive_pic_fusion_flag is equal to 1 and ChromaFormatIdc is not equal to 0: inputBaseY, inputBaseCb, inputBaseCr, inputDriveY, inputDriveCb, inputDriveCr , inputBaseKeyPoint, inputBaseMatrix,, inputDriveKeyPoint, inputDriveMatrix [0108] Outputs of GenerativeNN( ) are: – A luma sample array genY – When ChromaFormatIdc is not equal to 0, two chroma sample arrays genCb and genCr. [0109] The process StoreOutputTensors( ) for deriving the output is specified as follows: when gfv_base_pic_flag is equal to 0, the output sample array outYPic[ x ][ y ], outCbPic[ x ][ y ], and outCrPic[ x ][ y ] are derived as follows: for(x=0; x< CroppedWidth; x++){ for(y=0; y< CroppedHeight; y++){ outputYPic[ x ][ y ] = OutY( genY[ x ][ y ] ) } } if(ChromaFormatIdc != 0) { for(x=0; x< CroppedWidth/ SubWidthC; x++){ for(y=0; y< CroppedHeight/ SubHeightC; y++){ outputCbPic[ x ][ y ] = OutC( genCb[ x ][ y ] ) outputCrPic[ x][ y ] = OutC( genCr[ x ][ y ] ) } } } when gfv_base_pic_flag is equal to 1, the output sample array outYPic[ x ][ y ], outCbPic[ x ][ y ], and outCrPic[ x ][ y ] are derived as follows: for(x=0; x< CroppedWidth; x++){ for(y=0; y< CroppedHeight; y++){ outputYPic[ x ][ y ] = baseCroppedYPic [ x ][ y ] } } if(ChromaFormatIdc != 0) { for(x=0; x< CroppedWidth/ SubWidthC; x++){ for(y=0; y< CroppedHeight/ SubHeightC; y++){ outputCbPic[ x ][ y ] = baseCroppedCbPic [ x ][ y ] outputCrPic[ x][ y ] = baseCroppedCbPic [ x ][ y ] } } } [0110] Where the functions OutY( ) and OutC( ) are specified as follows: OutY( x ) = Clip3( 0, ( 1 << BitDepth_Y ) – 1 , x * ( ( 1 << BitDepth_Y ) – 1 ) OutC( x ) = Clip3( 0, ( 1 << BitDepthC ) – 1 , x * ( ( 1 << BitDepthC ) – 1 ) 3.4. Generative face video enhancement SEI messages [0111] JVET-AH2032 [4] also includes the specification of the generative face video enhancement SEI message, as follows. 8.37.1 Generative face video enhancement SEI message syntax generative_face_video_enhancement ( payloadSize ) { Descriptor gfve_id ue(v) gfve_nn_reserved_zero_bit_b u(1) for( i = 0; more_data_in_payload( ); i++ ) [0112] The generative face video enhancement (GFVE) SEI message indicates enhancement facial parameters and specifies an enhancement network (also referred to as an enhancer network), denoted as EnhancerNN( ), that may be used to enhance the visual quality of the face pictures generated with GFV SEI message [0113] NOTE 1 – Enhancement facial parameters could be determined from source pictures prior to encoding. [0114] NOTE 2 – When the current picture is not a base picture, the GFV SEI message may be used to generate a face picture based the facial parameters conveyed by the GFV SEI message, and the GFVE SEI message may be further used to enhance the generated face picture to improve the visual quality. [0115] Use of this SEI message requires the definition of the following variables: – Input and output picture width and height in units of luma samples, denoted herein by CroppedWidth and CroppedHeight, respectively. – Luma sample array baseCroppedYPic and chroma sample arrays baseCroppedCbPic and baseCroppedCrPic for a decoded output picture, denoted as BasePicture, corresponding to a base picture. – Luma sample array genCroppedYPic and chroma sample arrays genCroppedCbPic and genCroppedCrPic for a generated picture with associated GFV SEI message, denoted as GenPicture, corresponding to a driving picture. – Bit depth BitDepthY for the luma sample array of the input and output pictures. – Bit depth BitDepthC for the chroma sample arrays, if any, of the input and output pictures. – A chroma format indicator, denoted herein by ChromaFormatIdc, as described in subclause 7.3. [0116] The variables SubWidthC and SubHeightC are derived from ChromaFormatIdc. [0117] gfve_id contains an identifying number that may be used to identify GFVE SEI message and specify a neural network that may be used as EnhancerNN( ). The value of gfve_id shall be in the range of 0 to 2³²− 2, inclusive. Values of gfve_id from 256 to 511, inclusive, and from 2³¹ to 2³²− 2, inclusive, are reserved for future use by ITU-T | ISO/IEC. Decoders conforming to this edition of this document encountering a GFVE SEI message with gfve_id in the range of 256 to 511, inclusive, or in the range of 2³¹ to 2³²− 2, inclusive, shall ignore the SEI message. [0118] gfve_gfv_id and gfve_gfv_cnt specifies gfv_id and gfv_cnt of the associated GFV SEI message. The associated GFV SEI message is a GFV SEI message in the same picture unit with the GFVE SEI message having gfv_id equal to gfve_gfv_id, gfv_cnt equal to gfve_gfv_cnt. The GFVE message is used to enhance the picture generated with the associated GFV SEI message. [0119] For a GFVE SEI message, the following applies: – The GFVE SEI message shall be present in the same picture unit with the associated GFV SEI message. And the associated GFV SEI message shall be precede the GFVE SEI message in the decoding order. When the associated GFV SEI message is not present in the picture unit containing the GFVE SEI message, the GFVE SEI message shall be ignored. – When a GFVE SEI message is the first GFVE SEI message with a particular value of gfve_id is present in an IRAP picture unit or in a picture unit that follows IRAP picture unit in output order and is not preceded in output order by any picture unit that follows the IRAP picture unit in output order and has a GFVE SEI message with that particular value of gfve_id, gfve_nn_present_flag shall be present and equal to 1. – If a GFV SEI message A is associated with a GFVE SEI message A, and a GFV SEI message B is associated with a GFVE SEI message B, and GFV SEI message A precede the GFV SEI message B in decoding order, the GFVE SEI A shall also precede GFVE SEI message B in decoding order. – If a GFVE SEI message A with gfve_gfv_id equal to gfveGfvIdA, gfve_gfv_cnt value equal to gfveGfvCntA, and a GFVE SEI message B with gfve_gfv_id equal to gfveGfvIdB, gfve_gfv_cnt value equal to gfveGfvCntB, are present in the same picture unit, and gfveGfvIdA is equal to gfveGfvIdB and gfveGfvCntA is less than gfveGfvCntB, the GFVE SEI message A shall precede the GFVE SEI message B in decoding order. – If a GFVE SEI message A with gfve_gfv_id equal to gfveGfvIdA, gfve_gfv_cnt value equal to gfveGfvCntA, and a GFV SEI message B with gfv_id equal to gfvIdB, gfv_cnt value equal to gfvCntB, are present in the same picture unit, if gfveGfvIdA is equal to gfvIdB, gfveGfvCntA is less than gfvCntB, the GFVE SEI message A shall precede the GFV SEI message B in decoding order. – When either of the following conditions is true, GFVE SEI messages shall have the same SEI payload content: – The GFVE SEI messages are present in the same picture unit, have gfve_nn_base_flag present and equal to 1 and have the same value of gfve_id, gfve_gfv_id, gfve_gfv_cnt. – The GFVE SEI messages are present in the same picture unit, have gfve_nn_base_flag not present and have the same value of gfve_id, gfve_gfv_id, gfve_gfv_cnt. [0120] gfve_nn_present_flag equal to 1 indicates a neural network that may be used as a EnhancerNN( ) is contained or indicated by the SEI message. gfve_nn_present_flag equal to 0 indicates a neural network that may be used as a EnhancerNN( ) is not contained or indicated by the SEI message. [0121] gfve_nn_base_flag, gfve_nn_mode_idc, gfve_nn_reserved_zero_bit_a, gfve_nn_tag_uri, gfve_nn_uri, gfve_nn_payload_byte[ i ] specify a neural network that may be used as a EnhancerNN( ). gfv_nn_base_flag, gfv_nn_mode_idc, gfv_nn_reserved_zero_bit_a, gfv_nn_tag_uri, gfv_nn_uri, gfv_nn_payload_byte[ i ] have the same syntax and semantics as nnpfc_base_flag, nnpfc_mode_idc, nnpfc_reserved_zero_bit_a, nnpfc_tag_uri, nnpfc_uri, nnpfc_payload_byte[ i ], respectively. [0122] gfve_matrix_element_precision_factor indicates quantization factor of matrix elements signalled in the SEI message. [0123] gfve_num_matrices_minus1 plus 1 specifies the number of matrices signalled in the SEI message. The value of gfv_num_matrices_minus1 shall be in the range of 0 to 2¹⁶ – 1, inclusive. [0124] gfve_matrix_height_minus1[ i ] plus 1 indicates the height of the i-th matrix. [0125] gfve_matrix_width_minus1[ i ] plus 1 indicates the width of the i-th matrix. [0126] gfve_matrix_element[ i ][ j ][ k ] is used to derive the value of the element at position (k, j) of the i- th matrix. [0127] gfve_matrix_element_sign_flag[ i ][ j ][ k ] indicates the sign of the matrix element at position (k, j) of the i-th matrix. [0128] The variable matrixElementVal[ i ][ j][ k ] representing the value of the matrix element at position (k, j) of the i-th matrix is derived as follows: m_{atrixElementVal[ i][ j ][ k ] = ^1 ' 2 ∗ gfve_matrix_element_sign_flag^ i ^^ j ^^ k ^^ ∗} ^^^^ ^ ^^ : ^^ ^ [0129] The following process is invoked for each GFVE SEI message to enhance the picture generated with the associated GFV SEI message: DeriveInputTensors( ) if(ChromaFormatIdc == 0 ) EnhancerNN( inputBaseY, inputGenY, inputMatrix) else EnhancerNN( inputBaseY, inputBaseCb, inputBaseCr, inputGenY, inputGenCb, inputGenCr, inputMatrix) } StoreOutputTensors( ) [0130] The process DeriveInputTensors( ) for deriving the inputs of EnhancerNN ( ) is specified as follows: [0131] The BasePicture input tensor inputBaseY, inputBaseCb and inputBaseCr are derived as follows: for( x = 0; x < CroppedWidth; x++ ) { for ( y = 0; y < CroppedHeight; y++ ) { inputBaseY[ x ][ y ] = InpY( baseCroppedYPic[ x ][ y ] ) } } if (ChromaFormatIdc !=0) { for( x = 0; x < CroppedWidth/ SubWidthC; x++ ) { for ( y = 0; y < CroppedHeight/ SubHeightC; y++ ) { inputBaseCb[ x][ y ] = InpC( baseCroppedCbPic[ x][ y ] ) inputBaseCr[ x][ y ] = InpC( baseCroppedCrPic[ x ][ y ] ) } } } [0132] The GenPicture input tensor inputGenY, inputGenCb and inputGenCr are derived as follows: for( x = 0; x < CroppedWidth; x++ ) { for ( y = 0; y < CroppedHeight; y++ ) { inputGenY[ x ][ y ] = InpY( genCroppedYPic[ x ][ y ] ) } } if (ChromaFormatIdc !=0) { for( x = 0; x < CroppedWidth/ SubWidthC; x++ ) { for ( y = 0; y < CroppedHeight/ SubHeightC; y++ ) { inputGenCb[ x][ y ] = InpC( genCroppedCbPic[ x][ y ] ) inputGenCr[ x][ y ] = InpC( genCroppedCrPic[ x ][ y ] ) } } } [0133] The matrix input tensor inputMatrix is derived as follows: for ( i = 0; i <= gfve_num_matrices_minus1; i++ ) { for ( j = 0; j <= gfve_matrix_height_minus1[ i ]; j++) { for( k = 0; k <= gfve_matrix_width_minus1[ i ]; k++ ) { inputMatrix[ i ][ j ][ k ] = matrixElementVal[ i ][ j][ k ] } } } [0134] Where the functions InpY( ) and InpC( ) are specified as follows: InpY( x ) = x ÷ ( ( 1 << BitDepthY ) – 1 ) InpC( x ) = x ÷ ( ( 1 << BitDepthC ) – 1 ) [0135] EnhancerNN ( ) is a process to enhance the sample values of an generated picture that is generated with the associated GFV SEI message. Input values to EnhancerNN ( ) and output values from EnhancerNN ( ) are real numbers. [0136] Inputs to EnhancerNN () are: – When ChromaFormatIdc is equal to 0: inputBaseY, inputGenY, inputMatrix – When ChromaFormatIdc is not equal to 1: inputBaseY, inputBaseCb, inputBaseCr, inputGenY, inputGenCb, inputGenCr, inputMatrix [0137] Outputs of EnhancerNN ( ) are: – A luma sample array enhance – When ChromaFormatIdc is not equal to 0, two chroma sample arrays enhanceCb and enhanceCr. [0138] The process StoreOutputTensors( ) for deriving the output is specified as follows: [0139] The output sample array outYPic[ x ][ y ], outCbPic[ x ][ y ], and outCrPic[ x ][ y ] are derived as follows: for(x=0; x< CroppedWidth; x++){ for(y=0; y< CroppedHeight; y++){ outputYPic[ x ][ y ] = OutY(enhanceY[ x ][ y ]) } } if(ChromaFormatIdc != 0) { for(x=0; x< CroppedWidth/ SubWidthC; x++){ for(y=0; y< CroppedHeight/ SubHeightC; y++){ outputCbPic[ x ][ y ] = OutC(enhanceCb[ x ][ y ]) outputCrPic[ x][ y ] = OutC(enhanceCr[ x ][ y ]) } } } [0140] Where the functions OutY( ) and OutC( ) are specified as follows: OutY( x ) = Clip3( 0, ( 1 << BitDepth_Y ) – 1 , x * ( ( 1 << BitDepth_Y ) – 1 ) OutC( x ) = Clip3( 0, ( 1 << BitDepth_C ) – 1 , x * ( ( 1 << BitDepth_C ) – 1 ) 4. Technical problems solved by disclosed technical solutions [0141] An example design of the generative face video (GFV) SEI message and the generative face video enhancement (GFVE) SEI message in JVET-AH2032 [4] has the following problems: [0142] First, it is currently specified that, when a GFVE SEI message is the first GFVE SEI message with a particular value of gfve_id is present in an IRAP picture unit or in a picture unit that follows IRAP picture unit in output order and is not preceded in output order by any picture unit that follows the IRAP picture unit in output order and has a GFVE SEI message with that particular value of gfve_id, gfve_nn_present_flag shall be present and equal to 1. However, there is no need to require gfve_nn_present_flag to be present and equal to 1 for a GFVE SEI message in a picture unit that is not an IRAP picture unit. Furthermore, when an IRAP picture unit contains multiple GFVE SEI messages with a particular value of gfve_id and different values of gfve_gfv_cnt, there is no need to require gfve_nn_present_flag to be present and equal to 1 for all those GFVE SEI messages. [0143] Second, value ranges are missing for the ue(v)-coded syntax elements gfve_matrix_element_precision_factor, gfve_matrix_height_minus1[ i ], gfve_matrix_width_minus1[ i ], gfve_matrix_element[ i ][ j ][ k ], and gfv_matrix_element_int[ i ][ j ][ k ][ m ]. 4. A listing of solutions and embodiments [0144] To solve the above-described problems, methods as summarized below are disclosed. The aspects should be considered as examples to explain the general concepts and should not be interpreted in a narrow way. Furthermore, these examples can be applied individually or combined in any manner. 1) To solve problem 1, in one example, it is specified that, when a GFVE SEI message with gfve_gfv_cnt equal to 0 is present in an IRAP picture unit, gfve_nn_present_flag shall be present and equal to 1. a. In one example, alternatively, it is specified that, when a GFVE SEI message is present in an IRAP picture unit, gfve_nn_present_flag shall be present and equal to 1. b. In one example, alternatively, it is specified that, when a GFVE SEI message with gfve_gfv_cnt equal to 0 and a particular value of gfve_id is present in an IRAP picture unit or in a picture unit that follows an IRAP picture unit in output order and is not preceded in output order by any picture unit that follows the IRAP picture unit in output order and has a GFVE SEI message with that particular value of gfve_id, gfve_nn_present_flag shall be present and equal to 1. c. In one example, alternatively, it is specified that, when a GFVE SEI message with gfve_gfv_cnt equal to 0 is present in the first picture unit of a CLVS in decoding order, gfve_nn_present_flag shall be present and equal to 1. d. In one example, alternatively, it is specified that, when a GFVE SEI message is present in the first picture unit of a CLVS in decoding order, gfve_nn_present_flag shall be present and equal to 1. e. In one example, alternatively, it is specified that, when a GFVE SEI message with gfve_gfv_cnt equal to 0 and a particular value of gfve_id is present in the first picture unit firstPU of a CLVS in decoding order or in a picture unit that follows the picture unit firstPU in output order and is not preceded in output order by any picture unit that follows the picture unit firstPU in output order and has a GFVE SEI message with that particular value of gfve_id, gfve_nn_present_flag shall be present and equal to 1. 2) To solve problem 2, in one example, it is specified that, the value of gfve_matrix_element_precision_factor shall be in the range of 0 to N, inclusive, where N is an integer greater than 0. a. In one example, N is equal to 32. b. In one example, N is equal to 16. 3) To solve problem 2, in one example, it is specified that, the value of gfve_matrix_height_minus1[ i ] shall be in the range of 0 to N, inclusive, where N is an integer greater than 0. a. In one example, N is equal to 2⁸ − 1. 4) To solve problem 2, in one example, it is specified that, the value of gfve_matrix_width_minus1[ i ] shall be in the range of 0 to N, inclusive, where N is an integer greater than 0. a. In one example, N is equal to 2⁸ − 1. 5) To solve problem 2, in one example, it is specified that, the value of gfve_matrix_element[ i ][ j ][ k ] shall be in the range of 0 to N, inclusive, where N is an integer greater than 0. a. In one example, N is equal to 2³² − 2. b. In one example, N is equal to 2¹⁶ − 1. 6) To solve problem 2, in one example, it is specified that, the value of gfv_matrix_element_int[ i ][ j ][ k ][ m ] shall be in the range of 0 to N, inclusive, where N is an integer greater than 0. a. In one example, N is equal to 2³² − 2. b. In one example, N is equal to 2¹⁶ − 1. [0145] In the preceding discussion, the following references are referred to at times in shorthand fashion: [1] ITU-T and ISO/IEC, “High efficiency video coding”, Rec. ITU-T H.265 | ISO/IEC 23008-2 (in force edition). [2] ITU-T and ISO/IEC, “Versatile Video Coding”, Rec. ITU-T H.266 | ISO/IEC 23090-3. [3] ITU-T and ISO/IEC, “Versatile Supplemental Enhancement Information Messages for Coded Video Bitstreams”, Rec. ITU-T Rec. H.274 | ISO/IEC 23002-7. [4] S. McCarthy, J. Boyce, J. Chen, S. Deshpande, M. M. Hannuksela, Hendry (eds), “Technologies under consideration for future extensions of VSEI (version 4),” JVET output document JVET-AH2032, publicly available online herein: https://www.jvet-experts.org/doc_end_user/documents/34_Rennes/wg11/JVET- AH2032-v2.zip. [0146] FIG. 2 is a block diagram showing an example video processing system 4000 in which various techniques disclosed herein may be implemented. Various implementations may include some or all of the components of the system 4000. The system 4000 may include input 4002 for receiving video content. The video content may be received in a raw or uncompressed format, e.g., 8 or 10 bit multi-component pixel values, or may be in a compressed or encoded format. The input 4002 may represent a network interface, a peripheral bus interface, or a storage interface. Examples of network interface include wired interfaces such as Ethernet, passive optical network (PON), etc. and wireless interfaces such as Wi-Fi or cellular interfaces. [0147] The system 4000 may include a coding component 4004 that may implement the various coding or encoding methods described in the present document. The coding component 4004 may reduce the average bitrate of video from the input 4002 to the output of the coding component 4004 to produce a coded representation of the video. The coding techniques are therefore sometimes called video compression or video transcoding techniques. The output of the coding component 4004 may be either stored, or transmitted via a communication connected, as represented by the component 4006. The stored or communicated bitstream (or coded) representation of the video received at the input 4002 may be used by a component 4008 for generating pixel values or displayable video that is sent to a display interface 4010. The process of generating user-viewable video from the bitstream representation is sometimes called video decompression. Furthermore, while certain video processing operations are referred to as “coding” operations or tools, it will be appreciated that the coding tools or operations are used at an encoder and corresponding decoding tools or operations that reverse the results of the coding will be performed by a decoder. [0148] Examples of a peripheral bus interface or a display interface may include universal serial bus (USB) or high definition multimedia interface (HDMI) or DisplayPort, and so on. Examples of storage interfaces include serial advanced technology attachment (SATA), peripheral component interconnect (PCI), integrated drive electronics (IDE) interface, and the like. The techniques described in the present document may be embodied in various electronic devices such as mobile phones, laptops, smartphones or other devices that are capable of performing digital data processing and/or video display. [0149] FIG.3 is a block diagram of an example video processing apparatus 4100. The apparatus 4100 may be used to implement one or more of the methods described herein. The apparatus 4100 may be embodied in a smartphone, tablet, computer, Internet of Things (IoT) receiver, and so on. The apparatus 4100 may include one or more processors 4102, one or more memories 4104 and video processing circuitry 4106. The processor(s) 4102 may be configured to implement one or more methods described in the present document. The memory (memories) 4104 may be used for storing data and code used for implementing the methods and techniques described herein. The video processing circuitry 4106 may be used to implement, in hardware circuitry, some techniques described in the present document. In some embodiments, the video processing circuitry 4106 may be at least partly included in the processor 4102, e.g., a graphics co-processor. [0150] FIG.4 is a flowchart for an example method 4200 of video processing. The method 4200 performs a conversion between a visual media data and a bitstream according to a rule at step 4202. In various embodiments described herein, the rule specifies that when a generative face video enhancement (GFVE) supplemental enhancement information (SEI) message is present in an intra random access picture (IRAP) picture unit, a first syntax flag is required to be present and is equal to 1. The conversion may include encoding at an encoder, decoding at a decoder, or combinations thereof. [0151] It should be noted that the method 4200 can be implemented in an apparatus for processing video data comprising a processor and a non-transitory memory with instructions thereon, such as video encoder 4400, video decoder 4500, and/or encoder 4600. In such a case, the instructions upon execution by the processor, cause the processor to perform the method 4200. Further, the method 4200 can be performed by a non-transitory computer readable medium comprising a computer program product for use by a video coding device. The computer program product comprises computer executable instructions stored on the non-transitory computer readable medium such that when executed by a processor cause the video coding device to perform the method 4200. [0152] FIG.5 is a block diagram that illustrates an example video coding system 4300 that may utilize the techniques of this disclosure. The video coding system 4300 may include a source device 4310 and a destination device 4320. Source device 4310 generates encoded video data which may be referred to as a video encoding device. Destination device 4320 may decode the encoded video data generated by source device 4310 which may be referred to as a video decoding device. [0153] Source device 4310 may include a video source 4312, a video encoder 4314, and an input/output (I/O) interface 4316. Video source 4312 may include a source such as a video capture device, an interface to receive video data from a video content provider, and/or a computer graphics system for generating video data, or a combination of such sources. The video data may comprise one or more pictures. Video encoder 4314 encodes the video data from video source 4312 to generate a bitstream. The bitstream may include a sequence of bits that form a coded representation of the video data. The bitstream may include coded pictures and associated data. The coded picture is a coded representation of a picture. The associated data may include sequence parameter sets, picture parameter sets, and other syntax structures. I/O interface 4316 may include a modulator/demodulator (modem) and/or a transmitter. The encoded video data may be transmitted directly to destination device 4320 via I/O interface 4316 through network 4330. The encoded video data may also be stored onto a storage medium/server 4340 for access by destination device 4320. [0154] Destination device 4320 may include an I/O interface 4326, a video decoder 4324, and a display device 4322. I/O interface 4326 may include a receiver and/or a modem. I/O interface 4326 may acquire encoded video data from the source device 4310 or the storage medium/ server 4340. Video decoder 4324 may decode the encoded video data. Display device 4322 may display the decoded video data to a user. Display device 4322 may be integrated with the destination device 4320, or may be external to destination device 4320, which can be configured to interface with an external display device. [0155] Video encoder 4314 and video decoder 4324 may operate according to a video compression standard, such as the High Efficiency Video Coding (HEVC) standard, Versatile Video Coding (VVC) standard and other current and/or further standards. [0156] FIG.6 is a block diagram illustrating an example of video encoder 4400, which may be video encoder 4314 in the system 4300 illustrated in FIG.5. Video encoder 4400 may be configured to perform any or all of the techniques of this disclosure. The video encoder 4400 includes a plurality of functional components. The techniques described in this disclosure may be shared among the various components of video encoder 4400. In some examples, a processor may be configured to perform any or all of the techniques described in this disclosure. [0157] The functional components of video encoder 4400 may include a partition unit 4401, a prediction unit 4402 which may include a mode select unit 4403, a motion estimation unit 4404, a motion compensation unit 4405, an intra prediction unit 4406, a residual generation unit 4407, a transform processing unit 4408, a quantization unit 4409, an inverse quantization unit 4410, an inverse transform unit 4411, a reconstruction unit 4412, a buffer 4413, and an entropy encoding unit 4414. [0158] In other examples, video encoder 4400 may include more, fewer, or different functional components. In an example, prediction unit 4402 may include an intra block copy (IBC) unit. The IBC unit may perform prediction in an IBC mode in which at least one reference picture is a picture where the current video block is located. [0159] Furthermore, some components, such as motion estimation unit 4404 and motion compensation unit 4405 may be highly integrated, but are represented in the example of video encoder 4400 separately for purposes of explanation. [0160] Partition unit 4401 may partition a picture into one or more video blocks. Video encoder 4400 and video decoder 4500 may support various video block sizes. [0161] Mode select unit 4403 may select one of the coding modes, intra or inter, e.g., based on error results, and provide the resulting intra or inter coded block to a residual generation unit 4407 to generate residual block data and to a reconstruction unit 4412 to reconstruct the encoded block for use as a reference picture. In some examples, mode select unit 4403 may select a combination of intra and inter prediction (CIIP) mode in which the prediction is based on an inter prediction signal and an intra prediction signal. Mode select unit 4403 may also select a resolution for a motion vector (e.g., a sub-pixel or integer pixel precision) for the block in the case of inter prediction. [0162] To perform inter prediction on a current video block, motion estimation unit 4404 may generate motion information for the current video block by comparing one or more reference frames from buffer 4413 to the current video block. Motion compensation unit 4405 may determine a predicted video block for the current video block based on the motion information and decoded samples of pictures from buffer 4413 other than the picture associated with the current video block. [0163] Motion estimation unit 4404 and motion compensation unit 4405 may perform different operations for a current video block, for example, depending on whether the current video block is in an I slice, a P slice, or a B slice. [0164] In some examples, motion estimation unit 4404 may perform uni-directional prediction for the current video block, and motion estimation unit 4404 may search reference pictures of list 0 or list 1 for a reference video block for the current video block. Motion estimation unit 4404 may then generate a reference index that indicates the reference picture in list 0 or list 1 that contains the reference video block and a motion vector that indicates a spatial displacement between the current video block and the reference video block. Motion estimation unit 4404 may output the reference index, a prediction direction indicator, and the motion vector as the motion information of the current video block. Motion compensation unit 4405 may generate the predicted video block of the current block based on the reference video block indicated by the motion information of the current video block. [0165] In other examples, motion estimation unit 4404 may perform bi-directional prediction for the current video block, motion estimation unit 4404 may search the reference pictures in list 0 for a reference video block for the current video block and may also search the reference pictures in list 1 for another reference video block for the current video block. Motion estimation unit 4404 may then generate reference indexes that indicate the reference pictures in list 0 and list 1 containing the reference video blocks and motion vectors that indicate spatial displacements between the reference video blocks and the current video block. Motion estimation unit 4404 may output the reference indexes and the motion vectors of the current video block as the motion information of the current video block. Motion compensation unit 4405 may generate the predicted video block of the current video block based on the reference video blocks indicated by the motion information of the current video block. [0166] In some examples, motion estimation unit 4404 may output a full set of motion information for decoding processing of a decoder. In some examples, motion estimation unit 4404 may not output a full set of motion information for the current video. Rather, motion estimation unit 4404 may signal the motion information of the current video block with reference to the motion information of another video block. For example, motion estimation unit 4404 may determine that the motion information of the current video block is sufficiently similar to the motion information of a neighboring video block. [0167] In one example, motion estimation unit 4404 may indicate, in a syntax structure associated with the current video block, a value that indicates to the video decoder 4500 that the current video block has the same motion information as another video block. [0168] In another example, motion estimation unit 4404 may identify, in a syntax structure associated with the current video block, another video block and a motion vector difference (MVD). The motion vector difference indicates a difference between the motion vector of the current video block and the motion vector of the indicated video block. The video decoder 4500 may use the motion vector of the indicated video block and the motion vector difference to determine the motion vector of the current video block. [0169] As discussed above, video encoder 4400 may predictively signal the motion vector. Two examples of predictive signaling techniques that may be implemented by video encoder 4400 include advanced motion vector prediction (AMVP) and merge mode signaling. [0170] Intra prediction unit 4406 may perform intra prediction on the current video block. When intra prediction unit 4406 performs intra prediction on the current video block, intra prediction unit 4406 may generate prediction data for the current video block based on decoded samples of other video blocks in the same picture. The prediction data for the current video block may include a predicted video block and various syntax elements. [0171] Residual generation unit 4407 may generate residual data for the current video block by subtracting the predicted video block(s) of the current video block from the current video block. The residual data of the current video block may include residual video blocks that correspond to different sample components of the samples in the current video block. [0172] In other examples, there may be no residual data for the current video block for the current video block, for example in a skip mode, and residual generation unit 4407 may not perform the subtracting operation. [0173] Transform processing unit 4408 may generate one or more transform coefficient video blocks for the current video block by applying one or more transforms to a residual video block associated with the current video block. [0174] After transform processing unit 4408 generates a transform coefficient video block associated with the current video block, quantization unit 4409 may quantize the transform coefficient video block associated with the current video block based on one or more quantization parameter (QP) values associated with the current video block. [0175] Inverse quantization unit 4410 and inverse transform unit 4411 may apply inverse quantization and inverse transforms to the transform coefficient video block, respectively, to reconstruct a residual video block from the transform coefficient video block. Reconstruction unit 4412 may add the reconstructed residual video block to corresponding samples from one or more predicted video blocks generated by the prediction unit 4402 to produce a reconstructed video block associated with the current block for storage in the buffer 4413. [0176] After reconstruction unit 4412 reconstructs the video block, the loop filtering operation may be performed to reduce video blocking artifacts in the video block. [0177] Entropy encoding unit 4414 may receive data from other functional components of the video encoder 4400. When entropy encoding unit 4414 receives the data, entropy encoding unit 4414 may perform one or more entropy encoding operations to generate entropy encoded data and output a bitstream that includes the entropy encoded data. [0178] FIG.7 is a block diagram illustrating an example of video decoder 4500 which may be video decoder 4324 in the system 4300 illustrated in FIG.5. The video decoder 4500 may be configured to perform any or all of the techniques of this disclosure. In the example shown, the video decoder 4500 includes a plurality of functional components. The techniques described in this disclosure may be shared among the various components of the video decoder 4500. In some examples, a processor may be configured to perform any or all of the techniques described in this disclosure. [0179] In the example shown, video decoder 4500 includes an entropy decoding unit 4501, a motion compensation unit 4502, an intra prediction unit 4503, an inverse quantization unit 4504, an inverse transformation unit 4505, a reconstruction unit 4506, and a buffer 4507. Video decoder 4500 may, in some examples, perform a decoding pass generally reciprocal to the encoding pass described with respect to video encoder 4400. [0180] Entropy decoding unit 4501 may retrieve an encoded bitstream. The encoded bitstream may include entropy coded video data (e.g., encoded blocks of video data). Entropy decoding unit 4501 may decode the entropy coded video data, and from the entropy decoded video data, motion compensation unit 4502 may determine motion information including motion vectors, motion vector precision, reference picture list indexes, and other motion information. Motion compensation unit 4502 may, for example, determine such information by performing the AMVP and merge mode. [0181] Motion compensation unit 4502 may produce motion compensated blocks, possibly performing interpolation based on interpolation filters. Identifiers for interpolation filters to be used with sub-pixel precision may be included in the syntax elements. [0182] Motion compensation unit 4502 may use interpolation filters as used by video encoder 4400 during encoding of the video block to calculate interpolated values for sub-integer pixels of a reference block. Motion compensation unit 4502 may determine the interpolation filters used by video encoder 4400 according to received syntax information and use the interpolation filters to produce predictive blocks. [0183] Motion compensation unit 4502 may use some of the syntax information to determine sizes of blocks used to encode frame(s) and/or slice(s) of the encoded video sequence, partition information that describes how each macroblock of a picture of the encoded video sequence is partitioned, modes indicating how each partition is encoded, one or more reference frames (and reference frame lists) for each inter coded block, and other information to decode the encoded video sequence. [0184] Intra prediction unit 4503 may use intra prediction modes for example received in the bitstream to form a prediction block from spatially adjacent blocks. Inverse quantization unit 4504 inverse quantizes, i.e., de- quantizes, the quantized video block coefficients provided in the bitstream and decoded by entropy decoding unit 4501. Inverse transform unit 4505 applies an inverse transform. [0185] Reconstruction unit 4506 may sum the residual blocks with the corresponding prediction blocks generated by motion compensation unit 4502 or intra prediction unit 4503 to form decoded blocks. If desired, a deblocking filter may also be applied to filter the decoded blocks in order to remove blockiness artifacts. The decoded video blocks are then stored in buffer 4507, which provides reference blocks for subsequent motion compensation/intra prediction and also produces decoded video for presentation on a display device. [0186] FIG. 8 is a schematic diagram of an example encoder 4600. The encoder 4600 is suitable for implementing the techniques of VVC. The encoder 4600 includes three in-loop filters, namely a deblocking filter (DF) 4602, a sample adaptive offset (SAO) 4604, and an adaptive loop filter (ALF) 4606. Unlike the DF 4602, which uses predefined filters, the SAO 4604 and the ALF 4606 utilize the original samples of the current picture to reduce the mean square errors between the original samples and the reconstructed samples by adding an offset and by applying a finite impulse response (FIR) filter, respectively, with coded side information signaling the offsets and filter coefficients. The ALF 4606 is located at the last processing stage of each picture and can be regarded as a tool trying to catch and fix artifacts created by the previous stages. [0187] The encoder 4600 further includes an intra prediction component 4608 and a motion estimation/compensation (ME/MC) component 4610 configured to receive input video. The intra prediction component 4608 is configured to perform intra prediction, while the ME/MC component 4610 is configured to utilize reference pictures obtained from a reference picture buffer 4612 to perform inter prediction. Residual blocks from inter prediction or intra prediction are fed into a transform (T) component 4614 and a quantization (Q) component 4616 to generate quantized residual transform coefficients, which are fed into an entropy coding component 4618. The entropy coding component 4618 entropy codes the prediction results and the quantized transform coefficients and transmits the same toward a video decoder (not shown). Quantization components output from the quantization component 4616 may be fed into an inverse quantization (IQ) components 4620, an inverse transform component 4622, and a reconstruction (REC) component 4624. The REC component 4624 is able to output images to the DF 4602, the SAO 4604, and the ALF 4606 for filtering prior to those images being stored in the reference picture buffer 4612. [0188] FIG.9 is a flowchart for an example method 4700 of video processing. The method 4700 determines a generative face video (GFV) supplemental enhancement information (SEI) message comprises a GFV matrix element integer value at matrix position m,k of a jth matrix with an ith matrix type (gfv_matrix_element_int[ i ][ j ][ k ][ m ]), where the gfv_matrix_element_int[ i ][ j ][ k ][ m ] shall be in the range of 0 to 2³² − 2, inclusiveat step 4702. A conversion between a visual media data and a bitstream is perfomed based on the GFV SEI message at step 4704. The conversion may include encoding at an encoder, decoding at a decoder, or combinations thereof. [0189] It should be noted that the method 4700 can be implemented in an apparatus for processing video data comprising a processor and a non-transitory memory with instructions thereon, such as video encoder 4400, video decoder 4500, and/or encoder 4600. In such a case, the instructions upon execution by the processor, cause the processor to perform the method 4700. Further, the method 4700 can be performed by a non-transitory computer readable medium comprising a computer program product for use by a video coding device. The computer program product comprises computer executable instructions stored on the non-transitory computer readable medium such that when executed by a processor cause the video coding device to perform the method 4700. [0190] A listing of solutions preferred by some examples is provided next. [0191] The following solutions show examples of techniques discussed herein. [0192] 1. A method for processing media data comprising: performing a conversion between a visual media data and a bitstream according to a rule, wherein the rule specifies that when a generative face video enhancement (GFVE) supplemental enhancement information (SEI) message is present in an intra random access picture (IRAP) picture unit, a first syntax flag is required to be present and is equal to 1. [0193] 2. The method of solution 1, wherein the rule further specifies that the first syntax flag is required to be present and is equal to 1 when a GFVE SEI message with a first syntax element equal to 0 is present in the IRAP picture unit. [0194] 3. The method of any of solutions 1-2, wherein the rule further specifies that the first syntax flag is required to be present and is equal to 1 when a GFVE SEI message with the first syntax element equal to 0 and a particular value of a second syntax element is present in: the IRAP picture unit; or a picture unit that follows the IRAP picture unit in output order and is not preceded in output order by any picture unit that follows the IRAP picture unit in output order and has a GFVE SEI message with the particular value of the second syntax element. [0195] 4. The method of any of solutions 1-3, wherein the rule further specifies that the first syntax flag is required to be present and is equal to 1 when a GFVE SEI message is present in a first picture unit of a coded layer video sequence (CLVS) in decoding order. [0196] 5. The method of any of solutions 1-4, wherein the rule further specifies that the first syntax flag is required to be present and is equal to 1 when a GFVE SEI message with the first syntax element equal to 0 is present in a first picture unit of a coded layer video sequence (CLVS) in decoding order. [0197] 6. The method of any of solutions 1-5, wherein the rule further specifies that the first syntax flag is required to be present and is equal to 1 when a GFVE SEI message with the first syntax element equal to 0 and a particular value of a second syntax element is present in: the first picture unit (first PU) of a CLVS in decoding order; or in a picture unit that follows the picture unit firstPU in output order and is not preceded in output order by any picture unit that follows the picture unit firstPU in output order and has a GFVE SEI message with the particular value of the second syntax element. [0198] 7. The method of any of solutions 1-6, wherein the first syntax element is gfve_gfv_cnt, and wherein the first syntax flag is gfve_nn_present_flag. [0199] 8. The method of any of solutions 1-7, wherein a third syntax element of the GFVE SEI message is gfve_matrix_element_precision_factor, wherein the rule specifies that a value of gfve_matrix_element_precision_factor is in a range of 0 to A, inclusive, and wherein A is an integer greater than 0. [0200] 9. The method of solution 8, wherein A is equal to 32 or 16. [0201] 10. The method of any of solutions 1-9, wherein a fourth syntax element of the GFVE SEI message is gfve_matrix_height_minus1[ i ], wherein the rule specifies that a value of gfve_matrix_height_minus1[ i ] is in a range of 0 to B, inclusive, and wherein B is an integer greater than 0. [0202] 11. The method of solution 10, wherein B is equal to 2⁸ – 1. [0203] 12. The method of any of solutions 1-11, wherein a fifth syntax element of the GFVE SEI message is gfve_matrix_width_minus1[ i ], wherein the rule specifies that a value of gfve_matrix_width_minus1[ i ] is in a range of 0 to C, inclusive, and wherein C is an integer greater than 0. [0204] 13. The method of solution 12, wherein C is equal to 2⁸ – 1. [0205] 14. The method of any of solutions 1-13, wherein a sixth syntax element of the GFVE SEI message is gfve_matrix_element[ i ][ j ][ k ], wherein the rule specifies that a value of gfve_matrix_element[ i ][ j ][ k ] is in a range of 0 to D, inclusive, and wherein D is an integer greater than 0. [0206] 15. The method of solution 14, wherein D is equal to 2³² – 2 or 2¹⁶ – 1. [0207] 16. The method of any of solutions 1-15, wherein a seventh syntax element of the GFVE SEI message is gfv_matrix_element_int[ i ][ j ][ k ][ m ], wherein the rule specifies that a value of gfv_matrix_element_int[ i ][ j ][ k ][ m ] is in a range of 0 to E, inclusive, and wherein E is an integer greater than 0. _[0208] 17. The method of solution 16, wherein E is equal to 2³² – 2 or 2¹⁶ – 1. [0209] 18. An apparatus for processing video data comprising: a processor; and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to perform the method of any of solutions 1-17. [0210] 19. A non-transitory computer readable medium comprising a computer program product for use by a video coding device, the computer program product comprising computer executable instructions stored on the non-transitory computer readable medium such that when executed by a processor cause the video coding device to perform the method of any of solutions 1-17. [0211] 20. A non-transitory computer-readable recording medium storing a bitstream of a video which is generated by a method performed by a video processing apparatus, wherein the method comprises: generating a bitstream according to a rule, wherein the rule specifies that when a generative face video enhancement (GFVE) supplemental enhancement information (SEI) message is present in an intra random access picture (IRAP) picture unit, a first syntax flag is required to be present and is equal to 1. [0212] 21. A method for storing bitstream of a video, comprising: generating a bitstream according to a rule, wherein the rule specifies that when a generative face video enhancement (GFVE) supplemental enhancement information (SEI) message is present in an intra random access picture (IRAP) picture unit, a first syntax flag is required to be present and is equal to 1, and wherein the method further comprises storing the bitstream in a non-transitory computer-readable recording medium [0213] 22. A method, apparatus, or system described in the present document. [0214] The following solutions show further examples of techniques discussed herein. [0215] 1. A method for processing media data comprising: determining a generative face video (GFV) supplemental enhancement information (SEI) message comprises a GFV matrix element integer value at matrix position m,k of a jth matrix with an ith matrix type (gfv_matrix_element_int[ i ][ j ][ k ][ m ]), where the gfv_matrix_element_int[ i ][ j ][ k ][ m ] shall be in the range of 0 to 232 − 2, inclusive; and performing a conversion between a visual media data and a bitstream based on the GFV SEI message. [0216] 2. The method of solution 1, further comprising determining a generative face video enhancement (GFVE) SEI message comprises a GFVE matrix height minus one for an ith matrix (gfve_matrix_height_minus1[ i ]), where the gfve_matrix_height_minus1[ i ] shall be in a range of 0 to N where N is an integer greater than zero. [0217] 3. The method of any of solutions 1-2, wherein N is equal to 210 − 1, inclusive. [0218] 4. The method of any of solutions 1-3, wherein the GFVE SEI message further comprises a GFVE matrix width minus one for an ith matrix (gfve_matrix_width_minus1[ i ]), where the gfve_matrix_width_minus1[ i ] shall be in a range of 0 to N where N is an integer greater than zero. [0219] 5. The method of any of solutions 1-4, wherein N is equal to 210 − 1, inclusive. [0220] 6. The method of any of solutions 1-5, wherein the GFVE SEI message further comprises a GFVE matrix element precision factor, where the GFVE matrix element precision factor shall be in a range of 0 to 31. [0221] 7. The method of any of solutions 1-6, wherein the GFVE matrix element precision factor is included in a GFVE matrix element precision factor minus one (gfve_matrix_element_precision_factor_minus1) syntax element. [0222] 8. The method of any of solutions 1-7, wherein when a GFVE SEI message with a GFVE GFV count (gfve_gfv_cnt) equal to 0 is present in an intra random access picture (IRAP) picture unit, a GFVE neural network present flag (gfve_nn_present_flag) is required to be present and is equal to 1. [0223] [0224] 9. The method of any of solutions 1-8, wherein when a GFVE SEI message is present in an IRAP picture unit, gfve_nn_present_flag shall be present and equal to 1. [0225] 10. The method of any of solutions 1-9, wherein when a GFVE SEI message with gfve_gfv_cnt equal to 0 and a particular value of GFVE identifier (gfve_id) is present in an IRAP picture unit or in a picture unit that follows an IRAP picture unit in output order and is not preceded in output order by any picture unit that follows the IRAP picture unit in output order and has a GFVE SEI message with the particular value of gfve_id, gfve_nn_present_flag shall be present and equal to 1. [0226] 11. The method of any of solutions 1-10, wherein when a GFVE SEI message with gfve_gfv_cnt equal to 0 is present in a first picture unit of a coded layer video sequence (CLVS) in decoding order, gfve_nn_present_flag shall be present and equal to 1. [0227] 12. The method of any of solutions 1-11, wherein when a GFVE SEI message is present in a first picture unit of a CLVS in decoding order, gfve_nn_present_flag shall be present and equal to 1. [0228] 13. The method of any of solutions 1-12, wherein when a GFVE SEI message with gfve_gfv_cnt equal to 0 and a particular value of gfve_id is present in a first picture unit (firstPU) of a CLVS in decoding order or in a picture unit that follows the firstPU in output order and is not preceded in output order by any picture unit that follows the firstPU in output order and has a GFVE SEI message with that particular value of gfve_id, gfve_nn_present_flag shall be present and equal to 1. [0229] 14. The method of any of solutions 1-13, wherein the GFVE SEI message comprises a GFVE matrix element of an ith matrix at position k,j (gfve_matrix_element[ i ][ j ][ k ]), where gfve_matrix_element[ i ][ j ][ k ] shall be in a range of 0 to N, inclusive, where N is an integer greater than 0. [0230] 15. The method of any of solutions 1-14, wherein the gfve_matrix_element[ i ][ j ][ k ] shall be in a range of 0 to 232 – 2. [0231] 16. The method of any of solutions 1-14, wherein the gfve_matrix_element[ i ][ j ][ k ] shall be in a range of 0 to 216 – 2. [0232] 17. The method of any of solutions 1-16, wherein the conversion includes encoding the visual media data into the bitstream. [0233] 18. The method of any of solutions 1-16, wherein the conversion includes decoding the visual media data from the bitstream. [0234] 19. An apparatus for processing video data comprising: a processor; and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to perform the method of any of solutions 1-18. [0235] 20. A non-transitory computer readable medium comprising a computer program product for use by a video coding device, the computer program product comprising computer executable instructions stored on the non-transitory computer readable medium such that when executed by a processor cause the video coding device to perform the method of any of solutions 1-18. [0236] 21. A non-transitory computer-readable recording medium storing a bitstream of a video which is generated by a method performed by a video processing apparatus, wherein the method comprises: determining a generative face video (GFV) supplemental enhancement information (SEI) message comprises a GFV matrix element integer value at matrix position m,k of a jth matrix with an ith matrix type (gfv_matrix_element_int[ i ][ j ][ k ][ m ]), where the gfv_matrix_element_int[ i ][ j ][ k ][ m ] shall be in the range of 0 to 232 − 2, inclusive; and generating a bitstream based on the determining. [0237] 22. A method for storing bitstream of a video comprising: determining a generative face video (GFV) supplemental enhancement information (SEI) message comprises a GFV matrix element integer value at matrix position m,k of a jth matrix with an ith matrix type (gfv_matrix_element_int[ i ][ j ][ k ][ m ]), where the gfv_matrix_element_int[ i ][ j ][ k ][ m ] shall be in the range of 0 to 232 − 2, inclusive; generating a bitstream based on the determining; and storing the bitstream in a non-transitory computer-readable recording medium. [0238] In the solutions described herein, an encoder may conform to the format rule by producing a coded representation according to the format rule. In the solutions described herein, a decoder may use the format rule to parse syntax elements in the coded representation with the knowledge of presence and absence of syntax elements according to the format rule to produce decoded video. [0239] In the present document, the term “video processing” may refer to video encoding, video decoding, video compression or video decompression. For example, video compression algorithms may be applied during conversion from pixel representation of a video to a corresponding bitstream representation or vice versa. The bitstream representation of a current video block may, for example, correspond to bits that are either co-located or spread in different places within the bitstream, as is defined by the syntax. For example, a macroblock may be encoded in terms of transformed and coded error residual values and also using bits in headers and other fields in the bitstream. Furthermore, during conversion, a decoder may parse a bitstream with the knowledge that some fields may be present, or absent, based on the determination, as is described in the above solutions. Similarly, an encoder may determine that certain syntax fields are or are not to be included and generate the coded representation accordingly by including or excluding the syntax fields from the coded representation. [0240] The disclosed and other solutions, examples, embodiments, modules and the functional operations described in this document can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this document and their structural equivalents, or in combinations of one or more of them. The disclosed and other embodiments can be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a computer readable medium for execution by, or to control the operation of, data processing apparatus. The computer readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a composition of matter effecting a machine-readable propagated signal, or a combination of one or more them. The term “data processing apparatus” encompasses all apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, or multiple processors or computers. The apparatus can include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them. A propagated signal is an artificially generated signal, e.g., a machine- generated electrical, optical, or electromagnetic signal, that is generated to encode information for transmission to suitable receiver apparatus. [0241] A computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, sub programs, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network. [0242] The processes and logic flows described in this document can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be performed by, and apparatus can also be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit). [0243] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read only memory or a random-access memory or both. The essential elements of a computer are a processor for performing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto optical disks, or optical disks. However, a computer need not have such devices. Computer readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto optical disks; and compact disc read-only memory (CD ROM) and Digital versatile disc-read only memory (DVD-ROM) disks. The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry. [0244] While this patent document contains many specifics, these should not be construed as limitations on the scope of any subject matter or of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular techniques. Certain features that are described in this patent document in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. [0245] Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Moreover, the separation of various system components in the embodiments described in this patent document should not be understood as requiring such separation in all embodiments. [0246] Only a few implementations and examples are described and other implementations, enhancements and variations can be made based on what is described and illustrated in this patent document. [0247] A first component is directly coupled to a second component when there are no intervening components, except for a line, a trace, or another medium between the first component and the second component. The first component is indirectly coupled to the second component when there are intervening components other than a line, a trace, or another medium between the first component and the second component. The term “coupled” and its variants include both directly coupled and indirectly coupled. The use of the term “about” means a range including ±10% of the subsequent number unless otherwise stated. [0248] While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and methods might be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted, or not implemented. [0249] In addition, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items shown or discussed as coupled may be directly connected or may be indirectly coupled or communicating through some interface, device, or intermediate component whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the spirit and scope disclosed herein.

Claims

CLAIMS What is claimed is: 1. A method for processing media data comprising: determining a generative face video (GFV) supplemental enhancement information (SEI) message comprises a GFV matrix element integer value at matrix position m,k of a jth matrix with an ith matrix type (gfv_matrix_element_int[ i ][ j ][ k ][ m ]), where the gfv_matrix_element_int[ i ][ j ][ k ][ m ] shall be in the range of 0 to 2³² − 2, inclusive; and performing a conversion between a visual media data and a bitstream based on the GFV SEI message.

2. The method of claim 1, further comprising determining a generative face video enhancement (GFVE) SEI message comprises a GFVE matrix height minus one for an ith matrix (gfve_matrix_height_minus1[ i ]), where the gfve_matrix_height_minus1[ i ] shall be in a range of 0 to N where N is an integer greater than zero.

3. The method of any of claims 1-2, wherein N is equal to 2¹⁰ − 1, inclusive.

4. The method of any of claims 1-3, wherein the GFVE SEI message further comprises a GFVE matrix width minus one for an ith matrix (gfve_matrix_width_minus1[ i ]), where the gfve_matrix_width_minus1[ i ] shall be in a range of 0 to N where N is an integer greater than zero.

5. The method of any of claims 1-4, wherein N is equal to 2¹⁰ − 1, inclusive.

6. The method of any of claims 1-5, wherein the GFVE SEI message further comprises a GFVE matrix element precision factor, where the GFVE matrix element precision factor shall be in a range of 0 to 31.

7. The method of any of claims 1-6, wherein the GFVE matrix element precision factor is included in a GFVE matrix element precision factor minus one (gfve_matrix_element_precision_factor_minus1) syntax element.

8. The method of any of claims 1-7, wherein when a GFVE SEI message with a GFVE GFV count (gfve_gfv_cnt) equal to 0 is present in an intra random access picture (IRAP) picture unit, a GFVE neural network present flag (gfve_nn_present_flag) is required to be present and is equal to 1.

9. The method of any of claims 1-8, wherein when a GFVE SEI message is present in an IRAP picture unit, gfve_nn_present_flag shall be present and equal to 1.

10. The method of any of claims 1-9, wherein when a GFVE SEI message with gfve_gfv_cnt equal to 0 and a particular value of GFVE identifier (gfve_id) is present in an IRAP picture unit or in a picture unit that follows an IRAP picture unit in output order and is not preceded in output order by any picture unit that follows the IRAP picture unit in output order and has a GFVE SEI message with the particular value of gfve_id, gfve_nn_present_flag shall be present and equal to 1.

11. The method of any of claims 1-10, wherein when a GFVE SEI message with gfve_gfv_cnt equal to 0 is present in a first picture unit of a coded layer video sequence (CLVS) in decoding order, gfve_nn_present_flag shall be present and equal to 1.

12. The method of any of claims 1-11, wherein when a GFVE SEI message is present in a first picture unit of a CLVS in decoding order, gfve_nn_present_flag shall be present and equal to 1.

13. The method of any of claims 1-12, wherein when a GFVE SEI message with gfve_gfv_cnt equal to 0 and a particular value of gfve_id is present in a first picture unit (firstPU) of a CLVS in decoding order or in a picture unit that follows the firstPU in output order and is not preceded in output order by any picture unit that follows the firstPU in output order and has a GFVE SEI message with that particular value of gfve_id, gfve_nn_present_flag shall be present and equal to 1.

14. The method of any of claims 1-13, wherein the GFVE SEI message comprises a GFVE matrix element of an ith matrix at position k,j (gfve_matrix_element[ i ][ j ][ k ]), where gfve_matrix_element[ i ][ j ][ k ] shall be in a range of 0 to N, inclusive, where N is an integer greater than 0.

15. The method of any of claims 1-14, wherein the gfve_matrix_element[ i ][ j ][ k ] shall be in a range of 0 to 2³² – 2.

16. The method of any of claims 1-14, wherein the gfve_matrix_element[ i ][ j ][ k ] shall be in a range of 0 to 2¹⁶ – 2.

17. The method of any of claims 1-16, wherein the conversion includes encoding the visual media data into the bitstream.

18. The method of any of claims 1-16, wherein the conversion includes decoding the visual media data from the bitstream.

19. An apparatus for processing video data comprising: a processor; and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to perform the method of any of claims 1-18.

20. A non-transitory computer readable medium comprising a computer program product for use by a video coding device, the computer program product comprising computer executable instructions stored on the non- transitory computer readable medium such that when executed by a processor cause the video coding device to perform the method of any of claims 1-18.

21. A non-transitory computer-readable recording medium storing a bitstream of a video which is generated by a method performed by a video processing apparatus, wherein the method comprises: determining a generative face video (GFV) supplemental enhancement information (SEI) message comprises a GFV matrix element integer value at matrix position m,k of a jth matrix with an ith matrix type (gfv_matrix_element_int[ i ][ j ][ k ][ m ]), where the gfv_matrix_element_int[ i ][ j ][ k ][ m ] shall be in the range of 0 to 2³² − 2, inclusive; and generating a bitstream based on the determining.

22. A method for storing bitstream of a video comprising: determining a generative face video (GFV) supplemental enhancement information (SEI) message comprises a GFV matrix element integer value at matrix position m,k of a jth matrix with an ith matrix type (gfv_matrix_element_int[ i ][ j ][ k ][ m ]), where the gfv_matrix_element_int[ i ][ j ][ k ][ m ] shall be in the range of 0 to 2³² − 2, inclusive; generating a bitstream based on the determining; and storing the bitstream in a non-transitory computer-readable recording medium.