METHODS FOR DETERMINING THE SYNTHESIS FOR DYNAMIC MESH ENCODERS AND THEIR SUBCOMPONENTS

Abstract

The invention relates to a method by which some implementation scheme includes: obtaining a volumetric video bitstream, such that the volumetric video bitstream comprises at least one sub-bitstream, and such that the volumetric video bitstream also comprises a set of parameters providing information describing at least one such sub-bitstream; based on the information describing, selecting a decoder configuration to decode at least one such sub-bitstream; and decoding at least one such sub-bitstream using the selected decoder configuration.

Description

METHODS TO DEFINE PROFILES FOR DYNAMIC MESH CODEC AND ITS SUBCOMPONENTSCROSS-REFERENCE

[0001] This application claims the priority of European Patent Application No. 23306750.3, filed 10 October 2023, entitled “Methods to Define Profiles for Dynamic Mesh Codec and its Sub-Components,” which is incorporated herein by reference in its entirety.BACKGROUND

[0002] Visual volumetric video-based coding (V3C) is described in ISO / IEC 23090-5:2021 , Information technology — Coded representation of immersive media — Part 5: Visual volumetric video-based coding (V3C) and video-based point cloud compression (V-PCC). Video-based dynamic mesh coding (V-DMC) is a framework for compressing dynamic meshes that is being developed by extending V3C. The V-DMC framework may involve different attributes specified for a dynamic mesh sequence. In V-DMC, the underlying static mesh codec may decode mesh attributes per face or per vertex. These attributes may provide additional information about the static mesh e.g., color, texture coordinates, normals, reflectance information, transparency information, and / or user-defined attributes.

[0003] For V-DMC, a framework is developed by extending V3C. V3C is described at ISO / IEC 23090-5:2021 , Information technology — Coded representation of immersive media — Part 5: Visual volumetric video-based coding (V3C) and video-based point cloud compression (V- PCC).

[0004] The attributes from the static mesh codec may further be used by the basemesh codec. A basemesh bitstream is further encapsulated in a V3C bitstream. The hierarchical structure of a V-DMC bitstream is shown in FIG. 1. An extension mechanism in the V3C bitstream may provide information about the type of attributes that a V3C bitstream / framework will use from the underlying basemesh codec. Additionally, the basemesh bitstream may provide a mechanism to provide information about the type of mesh attribute of interest from the underlying static mesh codec. FIG. 1 illustrates encapsulation of a different sub-bitstreams in a V-DMC bitstream.SUMMARY

[0005] A method according to some embodiments comprises: obtaining a volumetric video bitstream, wherein the volumetric video bitstream includes at least one sub-bitstream, and wherein the volumetric video bitstream further includes a parameter set that provides profile information for the at least one sub-bitstream; based on the profile information, selecting a decoder configuration for decoding the at least one sub-bitstream; and decoding the at least one sub-bitstream using the selected decoder configuration. In some embodiments, the volumetric video bitstream is a V3C bitstream, and wherein the parameter set is provided at the V3C level.

[0006] In some embodiments, at least one of the sub-bitstreams is a basemesh bitstream, and wherein the parameter set includes information indicating whether the basemesh bitstream encodes a static mesh or a dynamic mesh.

[0007] In some embodiments, the sub-bitstreams include a static mesh bitstream and a displacement bitstream, and the profile information indicates whether the displacement bitstream is coded using an arithmetic codec.

[0008] In some embodiments, the profile information includes information identifying a video codec to be used for decoding at least one of the sub-bitstreams.

[0009] Some embodiments include a flag signaled at the bitstream level, wherein the flag indicates whether the information identifying the video codec is signaled at the bitstream level or at a sub-bitstream level.

[0010] In some embodiments, the sub-bitstreams include at least a displacement bitstream and a texture attribute bitstream, and wherein the profile information identifies at least a first codec to be used for decoding the displacement bitstream and a second codec to be used for decoding the texture attribute bitstream.

[0011] In some embodiments, the information identifying the first codec and the second codec is an integer value.

[0012] In some embodiments, the first codec and the second codec are the same video codec. In other embodiments, the first codec is an arithmetic codec and the second codec is a video codec.

[0013] In some embodiments, the sub-bitstreams include a displacement bitstream, wherein the parameter set includes a video parameter set extension, and wherein the video parameter set extension identifies a codec to be used for decoding the displacement bitstream.

[0014] An apparatus according to some embodiments comprises one or more processors, the apparatus being configured to perform any of the methods described herein.

[0015] An apparatus according to some embodiments comprises at least one processor and a computer-readable medium storing instructions for performing any of the methods described herein.

[0016] A computer-readable medium according to some embodiments stores instructions for performing any of the methods described herein.

[0017] A signal according to some embodiments comprises a volumetric video bitstream, wherein the volumetric video bitstream includes at least one sub-bitstream, and wherein the volumetric video bitstream further includes a parameter set that provides profile information for the at least one sub-bitstream.

[0018] A method according to some embodiments comprising encoding in a signal any of the information, e.g. profile information, described herein.

[0019] Some embodiments include a computer-readable medium storing any of the information described herein.BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 is a schematic illustration of the encapsulation of different sub-bitstreams in a V-DMC bitstream

[0021] FIG. 2 is a functional block diagram of a system used in some embodiments described herein.

[0022] FIG. 3 is a functional block diagram of block-based video encoder, such as an encoder used for WC.

[0023] FIG. 4 is a functional block diagram of a block-based video decoder, such as a decoder used for WC.

[0024] FIG. 5 is a functional block diagram of a dynamic mesh encoder according to the MPEG V-DMC.

[0025] FIG. 6 is a functional block diagram of a dynamic mesh encoder according to the MPEG V-DMC.

[0026] FIG. 7 is a functional block diagram of a mesh decoder according to some embodiments.DETAILED DESCRIPTIONOverview of Example Systems

[0027] Example embodiments may be implemented using other systems, such as the system of FIG. 2. FIG. 2 is a block diagram of an example of a system in which various aspects and embodiments are implemented. System 1000 can be embodied as a device including the various components described below and is configured to perform one or more of the aspects described in this document. Examples of such devices, include, but are not limited to, various electronic devices such as personal computers, laptop computers, smartphones, tablet computers, digital multimedia set top boxes, digital television receivers, personal video recording systems, connected home appliances, and servers. Elements of system 1000, singly or in combination, can be embodied in a single integrated circuit (IC), multiple ICs, and / or discrete components. For example, in at least one embodiment, the processing and encoder / decoder elements of system 1000 are distributed across multiple ICs and / or discrete components. In various embodiments, the system 1000 is communicatively coupled to one or more other systems, or other electronic devices, via, for example, a communications bus or through dedicated input and / or output ports. In various embodiments, the system 1000 is configured to implement one or more of the aspects described in this document.

[0028] The system 1000 includes at least one processor 1010 configured to execute instructions loaded therein for implementing, for example, the various aspects described in this document. Processor 1010 can include embedded memory, input output interface, and various other circuitries as known in the art. The system 1000 includes at least one memory 1020 (e.g., a volatile memory device, and / or a non-volatile memory device). System 1000 includes a storage device 1040, which can include non-volatile memory and / or volatile memory, including, but not limited to, Electrically Erasable Programmable Read-Only Memory (EEPROM), Read-Only Memory (ROM), Programmable Read-Only Memory (PROM), Random Access Memory (RAM), Dynamic Random Access Memory (DRAM), Static Random Access Memory (SRAM), flash, magnetic disk drive, and / or optical disk drive. The storage device 1040 can include an internal storage device, an attached storage device (including detachable and non-detachable storage devices), and / or a network accessible storage device, as non-limiting examples.

[0029] System 1000 includes an encoder / decoder module 1030 configured, for example, to process data to provide an encoded or decoded mesh, and the encoder / decoder module 1030 can include its own processor and memory. The encoder / decoder module 1030 represents module(s) that can be included in a device to perform the encoding and / or decoding functions. As is known, a device can include one or both of the encoding and decoding modules.Additionally, encoder / decoder module 1030 can be implemented as a separate element of system 1000 or can be incorporated within processor 1010 as a combination of hardware and software as known to those skilled in the art.

[0030] Program code to be loaded onto processor 1010 or encoder / decoder 1030 to perform the various aspects described in this document can be stored in storage device 1040 and subsequently loaded onto memory 1020 for execution by processor 1010. In accordance with various embodiments, one or more of processor 1010, memory 1020, storage device 1040, and encoder / decoder module 1030 can store one or more of various items during the performance of the processes described in this document. Such stored items can include, but are not limited to, the input mesh, the decoded mesh or portions of the decoded mesh, the bitstream, matrices, variables, and intermediate or final results from the processing of equations, formulas, operations, and operational logic.

[0031] In some embodiments, memory inside of the processor 1010 and / or the encoder / decoder module 1030 is used to store instructions and to provide working memory for processing that is needed during encoding or decoding. In other embodiments, however, a memory external to the processing device (for example, the processing device can be either the processor 1010 or the encoder / decoder module 1030) is used for one or more of these functions. The external memory can be the memory 1020 and / or the storage device 1040, for example, a dynamic volatile memory and / or a non-volatile flash memory. In several embodiments, an external non-volatile flash memory is used to store the operating system of, for example, a television. In at least one embodiment, a fast external dynamic volatile memory such as a RAM is used as working memory for coding and decoding operations, such as for MPEG-2 (MPEG refers to the Moving Picture Experts Group, MPEG-2 is also referred to as ISO / IEC 13818, and 13818-1 is also known as H.222, and 13818-2 is also known as H.262), HEVC (HEVC refers to High Efficiency Video Coding, also known as H.265 and MPEG-H Part 2), or WC (Versatile Video Coding, a new standard being developed by JVET, the Joint Video Experts Team).

[0032] The input to the elements of system 1000 can be provided through various input devices as indicated in block 1130. Such input devices include, but are not limited to, (i) a radio frequency (RF) portion that receives an RF signal transmitted, for example, over the air by a broadcaster, (ii) a Component (COMP) input terminal (or a set of COMP input terminals), (iii) a Universal Serial Bus (USB) input terminal, and / or (iv) a High Definition Multimedia Interface (HDMI) input terminal.

[0033] In various embodiments, the input devices of block 1130 have associated respective input processing elements as known in the art. For example, the RF portion can be associatedwith elements suitable for (i) selecting a desired frequency (also referred to as selecting a signal, or band-limiting a signal to a band of frequencies), (ii) downconverting the selected signal, (iii) band-limiting again to a narrower band of frequencies to select (for example) a signal frequency band which can be referred to as a channel in certain embodiments, (iv) demodulating the downconverted and band-limited signal, (v) performing error correction, and (vi) demultiplexing to select the desired stream of data packets. The RF portion of various embodiments includes one or more elements to perform these functions, for example, frequency selectors, signal selectors, band-limiters, channel selectors, filters, downconverters, demodulators, error correctors, and demultiplexers. The RF portion can include a tuner that performs various of these functions, including, for example, downconverting the received signal to a lower frequency (for example, an intermediate frequency or a near-baseband frequency) or to baseband. In one set-top box embodiment, the RF portion and its associated input processing element receives an RF signal transmitted over a wired (for example, cable) medium, and performs frequency selection by filtering, downconverting, and filtering again to a desired frequency band. Various embodiments rearrange the order of the above-described (and other) elements, remove some of these elements, and / or add other elements performing similar or different functions. Adding elements can include inserting elements in between existing elements, such as, for example, inserting amplifiers and an analog-to-digital converter. In various embodiments, the RF portion includes an antenna.

[0034] Additionally, the USB and / or HDMI terminals can include respective interface processors for connecting system 1000 to other electronic devices across USB and / or HDMI connections. It is to be understood that various aspects of input processing, for example, Reed-Solomon error correction, can be implemented, for example, within a separate input processing IC or within processor 1010 as necessary. Similarly, aspects of USB or HDMI interface processing can be implemented within separate interface ICs or within processor 1010 as necessary. The demodulated, error corrected, and demultiplexed stream is provided to various processing elements, including, for example, processor 1010, and encoder / decoder 1030 operating in combination with the memory and storage elements to process the datastream as necessary for presentation on an output device.

[0035] Various elements of system 1000 can be provided within an integrated housing, Within the integrated housing, the various elements can be interconnected and transmit data therebetween using suitable connection arrangement 1140, for example, an internal bus as known in the art, including the Inter-IC (I2C) bus, wiring, and printed circuit boards.

[0036] The system 1000 includes communication interface 1050 that enables communication with other devices via communication channel 1060. The communication interface 1050 can include, but is not limited to, a transceiver configured to transmit and to receive data overcommunication channel 1060. The communication interface 1050 can include, but is not limited to, a modem or network card and the communication channel 1060 can be implemented, for example, within a wired and / or a wireless medium.

[0037] Data is streamed, or otherwise provided, to the system 1000, in various embodiments, using a wireless network such as a Wi-Fi network, for example IEEE 802.11 (IEEE refers to the Institute of Electrical and Electronics Engineers). The Wi-Fi signal of these embodiments is received over the communications channel 1060 and the communications interface 1050 which are adapted for Wi-Fi communications. The communications channel 1060 of these embodiments is typically connected to an access point or router that provides access to external networks including the Internet for allowing streaming applications and other over- the-top communications. Other embodiments provide streamed data to the system 1000 using a set-top box that delivers the data over the HDMI connection of the input block 1130. Still other embodiments provide streamed data to the system 1000 using the RF connection of the input block 1130. As indicated above, various embodiments provide data in a non-streaming manner. Additionally, various embodiments use wireless networks other than Wi-Fi, for example a cellular network or a Bluetooth network.

[0038] The system 1000 can provide an output signal to various output devices, including a display 1100, speakers 1110, and other peripheral devices 1120. The display 1100 of various embodiments includes one or more of, for example, a touchscreen display, an organic lightemitting diode (OLED) display, a curved display, and / or a foldable display. The display 1100 can be for a television, a tablet, a laptop, a cell phone (mobile phone), or other device. The display 1100 can also be integrated with other components (for example, as in a smart phone), or separate (for example, an external monitor for a laptop). The other peripheral devices 1120 include, in various examples of embodiments, one or more of a stand-alone digital video disc (or digital versatile disc) (DVR, for both terms), a disk player, a stereo system, and / or a lighting system. Various embodiments use one or more peripheral devices 1120 that provide a function based on the output of the system 1000. For example, a disk player performs the function of playing the output of the system 1000.

[0039] In various embodiments, control signals are communicated between the system 1000 and the display 1100, speakers 1110, or other peripheral devices 1120 using signaling such as AV.Link, Consumer Electronics Control (CEC), or other communications protocols that enable device-to-device control with or without user intervention. The output devices can be communicatively coupled to system 1000 via dedicated connections through respective interfaces 1070, 1080, and 1090. Alternatively, the output devices can be connected to system 1000 using the communications channel 1060 via the communications interface 1050. The display 1100 and speakers 1110 can be integrated in a single unit with the other componentsof system 1000 in an electronic device such as, for example, a television. In various embodiments, the display interface 1070 includes a display driver, such as, for example, a timing controller (T Con) chip.

[0040] The display 1100 and speaker 1110 can alternatively be separate from one or more of the other components, for example, if the RF portion of input 1130 is part of a separate set- top box. In various embodiments in which the display 1100 and speakers 1110 are external components, the output signal can be provided via dedicated output connections, including, for example, HDMI ports, USB ports, or COMP outputs.

[0041] The embodiments can be carried out by computer software implemented by the processor 1010 or by hardware, or by a combination of hardware and software. As a nonlimiting example, the embodiments can be implemented by one or more integrated circuits. The memory 1020 can be of any type appropriate to the technical environment and can be implemented using any appropriate data storage technology, such as optical memory devices, magnetic memory devices, semiconductor-based memory devices, fixed memory, and removable memory, as non-limiting examples. The processor 1010 can be of any type appropriate to the technical environment, and can encompass one or more of microprocessors, general purpose computers, special purpose computers, and processors based on a multi-core architecture, as non-limiting examples.Overview of Video Codecs

[0042] The systems and methods disclosed herein may be used in the coding of textured meshes, which may be dynamic textured meshes. In some embodiments, information representing the displacements of a dynamic mesh and / or information representing attributes of the mesh (e.g. texture information) may be coded using known video coding techniques. An overview of block-based video coding techniques that may be used in some embodiments is provided below.

[0043] The video coding standards HEVC and WC, among others, are built upon the blockbased hybrid video coding framework. FIG. 3 is a block diagram of a block-based hybrid video encoding system 200. Variations of this encoder 200 are contemplated, but the encoder 200 is described below for purposes of clarity without describing all expected variations.

[0044] Before being encoded, a video sequence may go through pre-encoding processing (204), for example, applying a color transform to an input color picture (e.g., conversion from RGB 4:4:4 to YCbCr 4:2:0), or performing a remapping of the input picture components in order to get a signal distribution more resilient to compression (for instance using a histogramequalization of one of the color components). Metadata can be associated with the preprocessing and attached to the bitstream.

[0045] The input video signal 202 including a picture to be encoded is partitioned (206) and processed block by block in units of, for example, CUs. Different CUs may have different sizes. In VTM-1.0, a CU can be up to 128x128 pixels. However, different from the HEVC which partitions blocks only based on quad-trees, in the VTM-1.0, a coding tree unit (CTU) is split into CUs to adapt to varying local characteristics based on quad / binary / ternary-tree. Additionally, the concept of multiple partition unit type in the HEVC is removed, such that the separation of CU, prediction unit (PU) and transform unit (TU) does not exist in the WC-1.0 anymore; instead, each CU is always used as the basic unit for both prediction and transform without further partitions. In the multi-type tree structure, a CTU is firstly partitioned by a quadtree structure. Then, each quad-tree leaf node can be further partitioned by a binary and ternary tree structure. Different splitting types may be used, such as quaternary partitioning, vertical binary partitioning, horizontal binary partitioning, vertical ternary partitioning, and horizontal ternary partitioning.

[0046] In the encoder of FIG. 3, spatial prediction (208) and / or temporal prediction (210) may be performed. Spatial prediction (or “intra prediction”) uses pixels from the samples of already coded neighboring blocks (which are called reference samples) in the same video picture / slice to predict the current video block. Spatial prediction reduces spatial redundancy inherent in the video signal. Temporal prediction (also referred to as “inter prediction” or “motion compensated prediction”) uses reconstructed pixels from the already coded video pictures to predict the current video block. Temporal prediction reduces temporal redundancy inherent in the video signal. A temporal prediction signal for a given CU may be signaled by one or more motion vectors (MVs) which indicate the amount and the direction of motion between the current CU and its temporal reference. Also, if multiple reference pictures are supported, a reference picture index may additionally be sent, which is used to identify from which reference picture in the reference picture store (212) the temporal prediction signal comes.

[0047] The mode decision block (214) in the encoder chooses the best prediction mode, for example based on a rate-distortion optimization method. This selection may be made after spatial and / or temporal prediction is performed. The intra / inter decision may be indicated by, for example, a prediction mode flag. The prediction block is subtracted from the current video block (216) to generate a prediction residual. The prediction residual is de-correlated using transform (218) and quantized (220). (For some blocks, the encoder may bypass both transform and quantization, in which case the residual may be coded directly without the application of the transform or quantization processes.) The quantized residual coefficients are inverse quantized (222) and inverse transformed (224) to form the reconstructed residual,which is then added back to the prediction block (226) to form the reconstructed signal of the CU. Further in-loop filtering, such as deblocking / SAO (Sample Adaptive Offset) filtering, may be applied (228) on the reconstructed CU to reduce encoding artifacts before it is put in the reference picture store (212) and used to code future video blocks. To form the output video bit-stream 230, coding mode (inter or intra), prediction mode information, motion information, and quantized residual coefficients are all sent to the entropy coding unit (108) to be further compressed and packed to form the bit-stream.

[0048] FIG. 4 gives a block diagram of a block-based video decoder 250. In the decoder 250, a bitstream is decoded by the decoder elements as described below. Video decoder 250 generally performs a decoding pass reciprocal to the encoding pass as described in FIG. 2A. The encoder 200 also generally performs video decoding as part of encoding video data.

[0049] In particular, the input of the decoder includes a video bitstream 252, which can be generated by video encoder 200. The video bit-stream 252 is first unpacked and entropy decoded at entropy decoding unit 254 to obtain transform coefficients, motion vectors, and other coded information. Picture partition information indicates how the picture is partitioned. The decoder may therefore divide (256) the picture according to the decoded picture partitioning information. The coding mode and prediction information are sent to either the spatial prediction unit 258 (if intra coded) or the temporal prediction unit 260 (if inter coded) to form the prediction block. The residual transform coefficients are sent to inverse quantization unit 262 and inverse transform unit 264 to reconstruct the residual block. The prediction block and the residual block are then added together at 266 to generate the reconstructed block. The reconstructed block may further go through in-loop filtering 268 before it is stored in reference picture store 270 for use in predicting future video blocks.

[0050] The decoded picture 272 may further go through post-decoding processing (274), for example, an inverse color transform (e.g. conversion from YCbCr 4:2:0 to RGB 4:4:4) or an inverse remapping performing the inverse of the remapping process performed in the preencoding processing (204). The post-decoding processing can use metadata derived in the pre-encoding processing and signaled in the bitstream. The decoded, processed video may be sent to a display device 276. The display device 276 may be a separate device from the decoder 250, or the decoder 250 and the display device 276 may be components of the same device.

[0051] Various methods and other aspects described in this disclosure can be used to modify modules of a video encoder 200 or decoder 250. Moreover, the systems and methods disclosed herein are not limited to WC or HEVC, and can be applied, for example, to other standards and recommendations, whether pre-existing or future-developed, and extensionsof any such standards and recommendations (including WC and HEVC). Unless indicated otherwise, or technically precluded, the aspects described in this disclosure can be used individually or in combination.Overview of Mesh Coding

[0052] FIG. 5 is a schematic block diagram of a mesh encoding process that may be employed in some embodiments. A source mesh model 302 is provided as an input mesh M(i) to the mesh encoding process. The source mesh model 302 is associated with a source texture map 304 that is proved as an input texture map A(i) to the encoding process. The input mesh is decimated at 306 to generate a base mesh m(i) with a reduced number of vertices, and a UV atlas is generated for the base mesh AT 308. The base mesh is quantized at 310 and encoded at 312, with the compressed base mesh data being multiplexed at 314 into a dynamic mesh bitstream. The compressed base mesh data is reconstructed at the encoder to generate reconstructed base mesh m’(i) with a static mesh decoder 316. The reconstructed base mesh is subdivided at 318 by adding new vertices. A subdivision surface fitting process is performed at 320 by comparing the subdivided base mesh with the input mesh M(i) to determine a set of displacements d(i) that deform the vertices of the subdivided base mesh to correspond more closely to the surfaces defined by the input mesh M(i). These displacements may be updated at 322 into updated displacements d’(i) based on difference between the original base mesh m(i) and the reconstructed base mesh m’(i). These updated displacements are encoded using a wavelet transform 324 that generates wavelet coefficients e’(i), which are quantized at 326 and packed at 328 into an image format. A time-varying series of images representing the wavelet coefficients may be encoded at 330 using conventional video encoding techniques, and the encoded video may be multiplexed at 314 with the data representing the compressed base mesh. At the encoder, the displacements are reconstructed from the encoded video through image unpacking 328, inverse quantization 330, and inverse wavelet transform 332 to generate a reconstructed set of displacements d”(i). A reconstructed base mesh M”(i) is obtained through inverse quantization at 334 of the reconstructed quantized base mesh m’(i), and the reconstructed base mesh M”(i) is subdivided at 336. A reconstructed deformed mesh DM(i) is generated at 338 by applying the reconstructed set of displacements d”(i) to the reconstructed base mesh m’(i). The reconstructed deformed mesh DM(i) is used as a destination mesh model 340 for the purpose of attribute transfer.

[0053] Using the reconstructed deformed mesh DM(i) (destination mesh model 340), the input mesh M(i) (source mesh model 302), and the input texture map A(i) (source texture map 304), an attribute transfer process is performed to provide attribute values for a destination texture map A’(i) that is associated with the reconstructed deformed mesh DM(i). Pixels in the texture map A’(i) that are not associated with any triangle of the reconstructed deformed mesh DM(i)may be filled using a padding process 342. A color space conversion 344 may be performed, a time-varying series of texture maps A’(i) may be encoded using conventional video encoding techniques 346, and the encoded video may be multiplexed at 314 into a bitstream 350 with the data representing the displacements and the compressed base mesh. Patch information 348 may also be multiplexed in the bitstream.

[0054] FIG. 6 illustrates an example of a mesh decoder. The mesh decoder demultiplexes different sub-bitstreams from, e.g. a V3C bitstream. The sub-bitstreams may include a subbitstream representing a static mesh, a sub-bitstream representing displacements, and one or more sub-bitstreams representing attributes. In the illustration of FIG. 6, the displacements sub-bitstream is illustrated as being decoded with a video decoder, but as discussed in greater detail below, different decoder configurations may be used depending on parameters received in the bitstream. For example, the decoder may be configured to use an arithmetic decoder in place of a video decoder for the coding of the displacements. In addition, where video coding is used, different decoder configurations may use different video codecs (such as AVC, HEVC, WC, and the like).Overview of Profiles

[0055] V3C profile decoding capability is defined by a combination of syntax elements ptl_profile_codec_group_idc and ptl_profile_toolset_idc that are present in the V3C parameter set. An optional syntax ptl_profile_reconstruction_idc defines the reconstruction capabilities.

[0056] The first two profile components together describe one of two conformance points for a V3C bitstream, referred to as conformance point A. ptl_profile_codec_group_idc describes the video decoding specifications and their profiles (e.g., Progressive High as specified in ISO / IEC 14496-10:2014:Annex A, Main or Main 10 as specified in ISO / IEC 23008- 2:2020:Annex A), referred to as the CodecGroup profile component, and ptl_profile_toolset_idc describes the V3C specific tools (e.g., use of EOM and PLR, etc.), referred to as the Toolset profile component. The Toolset profile component describes the bitstream syntax structure.

[0057] However, there is no profiling done for the V-DMC specification which is based on V3C. Profiling allows conformance to be achieved. Conformance is an important aspect in any decoder, including V-DMC. Therefore, it would be desirable for the specification ISO / IEC 23090-5 and ISO / IEC 23090-29 to be further extended to support profiling efforts.

[0058] ptl_profile_codec_group_idc identifies that all the video sub-bitstreams conform with the codec which is identified using the 4CC code of its stream format.

[0059] In cases where the content author wants to use different codecs for different subcomponents ofV3C, the only option currently is to use ptl_profile_codec_group_idc value 127. This relates to the use of codec code-points registered with the MP4 Registration Authority (MP4RA) to identify a specific codec.Overview of Basemesh Codec Identification

[0060] A V3C parameter set (VPS) extension, namely V3C parameter set V-DMC extension, exists to specify the V-DMC-specific parameters. One of the syntax elements in this extension is vps_ext_bmesh_data_substream_codec_id. The vps_ext_bmesh_data_substream_codec_id syntax element indicates the identifier of the codec used to compress the basemesh data for the atlas with atlas ID j. This codec may be identified through the profiles, a component codec mapping SEI message, or through means outside ISO / IEC 23090-5 and ISO / IEC 23090-29 specifications.

[0061] However, V3C profiles defined in Annex A of ISO / IEC 23090-5 do not provide codec information for the basemesh sub-stream. It would be desirable for Annex A of ISO / IEC 23090-5 to be extended to address the signaling of a basemesh codec, or for extensions to the profile codec group to be specified in ISO / IEC 23090-29.

[0062] The ISO / IEC 23090-29 and ISO / IEC 23090-14 specifications provide no mechanism to describe default codecs for all the different sub-components of a V-DMC V3C bitstream.Overview of Sub-Codec Identification in a Basemesh Codec

[0063] A basemesh codec is specified in Annex H of ISO / IEC 23090-29. The MPEG basemesh codec has two sub-codecs, namely the intra mesh codec and inter mesh codec. The codec for intra mesh sub-bitstream and inter mesh sub-bitstream are identified by the bmsps_intra_mesh_codec_id and bmsps_inter_mesh_codec_id syntax elements of the basemesh sequence parameter set, respectively. However, there is no indication of basemesh profiles as to which codecs for each intra mesh and inter mesh coding to be used depending on a profile chosen for a basemesh sub-bitstream.

[0064] The V-DMC specification provides no mechanism to describe default codecs for different sub-components of a basemesh bitstream.Overview of the Association of an Atlas with a Basemesh Bitstream

[0065] In the V3C specification, each sub-component is associated with an atlas with its corresponding atlasID. According to the syntax of the V3C parameter set, each atlas is associated with its sub-components, such as occupancy, geometric, and attributes, shownwith an asterisk (*) in the table below. However, the V3C extension is defined outside the scope of the vps_atlas_count loop, shown with a dagger (t) in the table below.

[0066] The current working draft of ISO / IEC 23090-29 does not consider the relationship between atlas and basemesh sub-bitstream.Overview of Example Embodiments

[0067] Currently, the profile group identifiers are not comparable with V3C extension for V- DMC. There is a strong need to describe profiling and corresponding codecs for different profiles of the sub-components of a V-DMC bitstream.

[0068] Some embodiments provide a mechanism to describe different V3C profiles for V- DMC. This involves describing profiles at the V3C level as well as the basemesh level. The V- DMC profile decoding capability is defined using a set of codecs and toolsets are described for different sub-components of a V-DMC bitstream. Further profiling of V3C for VDMC is also addressed. Section 1 , below describes embodiments providing a mechanism to define V3C profiles for V-DMC. Specifically, embodiments in Section 1.1 extend the profile toolsets component of a V3C profile for V-DMC. Embodiments in Section 1.2 extend the profile codec group component of a V3C profile for V-DMC. Embodiments in Section 1.3 extend the profile reconstruction component of a V3C profile for V-DMC. Embodiments in Section 1 .4 provide an alternative mechanism to describe displacement sub-bitstream information for V-DMC. Embodiments in Section 1 .5 provide an alternative mechanism to describe a profile codec group for V-DMC.

[0069] Some embodiments provide a mechanism to profile the basemesh codec in Annex H of ISO / IEC 23090-29. Section 2 describes example profile components such as profile toolset and profile codec group of the basemesh stream format.

[0070] Some embodiments provide a processing method to identify the atlasID and associate the atlas ID with the basemesh bitstream. Section 3 describes embodiments that associate an atlas with atlas ID to a basemesh bitstream. In case the VPS extension for V-DMC gets updated with new syntax elements to describe other mesh-specific sub-bitstreams, then the association with atlasID will still hold true.

[0071] The V3C specification offers a range of tools which are used in specific applications. However, some of the tools may not be used in other applications. A V3C-based mesh specification, e.g., V-DMC may be useful only for a subset of the functionalities defined by the V3C specification. A V-DMC implementation, in terms of encoder and decoder, complies with the functional requirements from the V3C specification.

[0072] Therefore, current embodiments provide a mechanism to contain and limit the supporting functionalities for encoder and decoder which are only of interest in the context of a V-DMC application. In the case of a generic V3C encoder and decoder, compliance with allV3C bitstreams, that is V-PCC, MIV and V-DMC, is desirable, and proper signaling of which bitstream is used is called for.(§ 1.1) Extending the Profile Toolset Component of V3C

[0073] Some applications call for the use of static or dynamic V-DMC bitstreams. For easier integration with current infrastructure and deployed hardware, it is beneficial to leverage the video coding technologies support in hardware. This translates to the use of video-coded subbitstreams, e.g., the displacement and texture attribute for a V-DMC bitstream along with basemesh sub-bitstream. At a high-level, this can be called a basic profile for V-DMC or, alternatively, V-DMC basic. A V-DMC may also contain a still V-DMC items with coding tools same as the V-DMC basic profile. This may be called V-DMC still profile.

[0074] In some other applications, the displacement bitstream may be coded using an arithmetic codec. Therefore, there is a complete change of toolset used to code one of the sub-components, namely the displacement sub-component for a V-DMC bitstream.

[0075] Some reserved values of ptl_profile_toolset_idc are used to specify a profile toolset for a V-DMC bitstream, e.g., values starting from 128 till value 140.

[0076] Toolset profile components for V3C extended V-DMC is identified through syntax elements, e.g., ptl_profile_toolset_idc and ptc_one_v3c_frame_only_flag. V3C reserved values for ptl_profile_toolet_idc are used to describe toolset profile for V-DMC bitstreams. The defined profiles in Table 1 are characterized as either dynamic or static.Table 1. Toolset profile components for V-DMC

[0077] As shown in Table 1 , a ptl_profile_toolset_idc value 128 specifies V-DMC basic profile. A V-DMC basic profile may incorporate a limited of functionalities such as the use of only attributes of type ATTR_TEXTURE for the V3C_AVD sub-component and the use of avideo codec for the displacement bitstream in the V3C_GVD sub-component. Further details are provided in Table 2, below.

[0078] There may be another profile toolset indicator, for example ptl_profile_toolset_idc value 129, which specifies a V-DMC basic profile but with an arithmetic codec used for coding the displacement component of V-DMC. An arithmetic codec may provide higher compression gain over native video compression tools. There may be a new V3C unit type, e.g., V3C_DPD, which identifies that the displacement information is coded using an arithmetic codec.

[0079] There may be another profile toolset indicator, for example ptl_profile_toolset_idc value 130, which specifies a V-DMC basic profile but with packed video support. This would allow to pack the texture attribute and video-based displacement information in a single video frame. This means that V3C_PVD is present in the bitstream and proper signaling is used to indicate that the texture and displacement data are not carried in V3C units of the type V3C_AVD and V3C_GVD or V3C_DPD, respectively, and that those types of sub-bitstreams are not present in the bitstream. This does not apply to the basemesh bitstream as the basemesh bitstream is coded using geometrical representation rather textural representation as used in VPCC.

[0080] Similarly, there may be another profile toolset indicator, for example ptl_profile_toolset_idc value 131 , which specifies a V-DMC bitstream which only includes basemesh and displacement components. That is, there are no texture attribute components in the V-DMC bitstream. This can be useful in cases where the only interest is to decode the geometry of the dynamic mesh but not to add a texture to decoded mesh. This means that V3C_AVD is not present in the bitstream.

[0081] There can be more profiles specified in Table 1 with additional ptl_profile_toolset_idc values, e.g., starting from 132. These extended profiles may indicate the use of specific tools which are not included in the V-DMC basic profiles. Note that the illustrative limitations below can be applied to the basic V-DMC profiles too.

[0082] There are some general syntax element restrictions, for instance:• The vuh_unit_type V3C_OVD is ignored for all V-DMC profiles and the V3C_BMD is included.• The V3C_CAD is excluded in Table 2 but may be present in future profiles.• The V3C GVD (for geometry) defined in V3C is included in the V-DMC basic, where it only represents a displacement bitstream that is coded with a video codec.• In a profile such as VDMC basic with arithmetic codec in Table 2, the V3C_GVD could also be used for displacement bitstream codec with an arithmetic coder, unless a new V3C_DPD is defined for displacement (here just for non-video-based coding).• asps_vmc_ext_subdivision_method is set to a value other than zero, indicating that subdivision is not allowed in all the profiles defined in Table 2. It is expected that some profiles may be defined which may not make use of subdivision. For example, in a lossless scenario, a high-resolution mesh is not decimated and is compressed as is. When the resulting mesh stream is decoded, there is no subdivision involved. In such a scenario, there may be no need to have displacement information from the displacement bitstream as the mesh is losslessly coded.• RAW patch data units may be present in the bitstream when asps_vmc_ext_direct_attribute_projection_enabled_flag is set to 1 and the patch projection information is signaled in a raw patch data unit for the attribute signaled in the attribute video data unit. In such a case, the asps_raw_patch_enabled_flag is set to 1 .• In simple profiles of V-DMC, only a texture-based attribute video is supported. This involves using at most one video decoder instance which is widely available in hardware video decoding solutions. To enable this functionality, ai_attribute_count is set to 0 for basic profiles as well as for a packed profile. The attribute type is restricted to ATTR_TEXTURE.

[0083] The V3C toolset profile components indicate the V-DMC basic, V-DMC basic with arithmetic codec for displacement, VDMC packed, V-DMC geometry only conforms to the syntax element restriction specified in Table 2. If a syntax element is not mentioned in Table 2, then the syntax element is not restricted through a toolset profile component. It is expected that other toolset profile components may be defined by the MPEG V-DMC group, in which case the newly defined profiles may be incorporated in to Table 2.

[0084] In future iterations of the specification, new syntax elements may be added to Table 2. Furthermore, there may be cases to further constrain the usage of certain tools in V3C. This can be done by further extending the profile_toolset_constraints_information() syntax structure, as well as other syntax elements, to provide additional syntax elements which constrain the toolset definition.Attribute video toolset constraintTable 2. Allowed syntax element values for the V-toolset profile components.(§ 1.2) Extending the profile codec group of V3CTo incorporate new sub-bitstreams such as the Basemesh bitstream, and an arithmetic coded displacement bitstream as specified in V-DMC, the V3C profile codec group may be extended. The extended V3C profile codec group identifies combinations of different sub-bitstream codecs.

[0085] In ISO / IEC 23090-5, ptl_profile_codec_group_idc indicates the codec group profile component to which the CVS conforms. The benefit of the ptl_profile_codec_group_idc is to indicate, for currently specified values other than 127, that all components / sub-bitstreams use the same codec. Currently, values for ptl_profile_codec_group_idc in range 5 - 126 are reserved identifiers.

[0086] The following embodiments use a set of values from the reserved range to describe the different combinations of different sub-bitstream codecs for the needs of V-DMC.

[0087] Example embodiments update the table in the V3C specification as shown in Table 3, with new material being indicated by a dagger (t).Table 3. Profile codec group components extended for V-DMC

[0088] In some embodiments, a range of at least ten values reserved for use in describing the ptl_profile_codec_group_idc for a V-DMC bitstream. The range may be extended further to provide more functionality. For example, the values from the reserved value of ptl_profile_codec_group_idc may be in the range 5 - 14 or the range 118 - 126 and are used to describe the different combinations of different sub-bitstream codecs for a V-DMC bitstream. The range of 5-14 is used as an example in Sections 1.2.1 through 1.2.4, below, to describe different codecs for sub-components of V3C-contained V-DMC bitstream.

[0089] In some embodiments, the profile codec group for a V-DMC bitstream is defined in a way that allows for the codec for each sub-component to be defined separately. This allows for a specific codec to be defined for each V-DMC sub-component. Example implementations of such embodiments are described in Sections 1 .2.1 through 1 .2.4. This is different from the profile codec group definitions as described in ISO / IEC 23090-5, where each sub-component is associated to only one codec in a profile codec group.(§ 1.2.1) MPEG Basemesh CodecIn one embodiment, the profile group from ptl_profile_codec_group_idc from values 5 to 14 calls for the use of Annex H: Basemesh codec in ISO / IEC 23090-29, such that the MPEG basemesh codec is used to code basemesh data in the V-DMC bitstream. This ensures that any V-DMC bitstream codes the basemesh information in the syntax provided by the MPEG basemesh codec. There is a possibility that the MPEG basemesh codec may be extracted as a separate specification from ISO / IEC 23090-29. In such a case, the reference to the extracted MPEG basemesh codec may be referred to as the mandatory basemesh codec in the profiles defined by the V-DMC bitstream.

[0090] It should be noted that even with ptl_profile_codec_group_idc set to 127, i.e., where codec mappings are provided using Component Codec Mapping (CCM) SEI message; the codec for basemesh codec cannot be set using the CCM SEI message in the V3C bitstream.

[0091] The texture attribute sub-component is coded using a video codec such as H.264 / AVC, HEVC, and others as shown in Table 5. Therefore, all the ptl_codec_group_idc values 5 to 14 identify that the texture attribute component conforms with the stream format of video decoders, as defined by the codec code points ‘avc3’, ‘hev1 ’, and ‘wi1’ registered with the MP4RA.

[0092] The displacement information is coded in the displacement sub-bitstream of a V3C bitstream. The identification of the displacement sub-bitstream can be either through V3C_GVD or V3C_DPD.

[0093] With ptl_codec_group_idc set to a value in the range 5 to 9, inclusive, the displacement sub-component is coded using a video codec such as H.264 / AVC, HEVC, or others as shown in Table 5. Therefore, for ptl_codec_group_idc values from 5 to 9, the displacement component conforms with the stream format of video decoder as defined by the codec code points, such as ‘avc3’, ‘hev1 ’ and ‘wi1’. V3C units that contain the displacement information use the V3C unit type V3C_GVD.

[0094] Alternatively, in some embodiments, the displacement sub-component may be coded using an arithmetic coding (AC) codec. The use of such codec provides benefits in terms of bitrate reduction compared to a traditional video encoder.

[0095] Therefore, in some embodiments, with ptl_codec_group_idc set to a value in the range 10 to 14, inclusive, the displacement sub-component is coded using an arithmetic coding codec such as Annex J in ISO / IEC 23090-29. Hence, in example embodiments, for ptl_codec_group_idc values from 10 to 14, the displacement sub-bitstream conforms with the stream format of an arithmetic decoder such as that defined in Annex J of ISO / IEC 23090-29, i.e., the MPEG AC decoder. (It is noted that a 4CC code for the MPEG AC decoder is yet to be defined, so the reference “Annex J” is used instead.)Table 4. Profile codec group component for VDMC with MPEG basemesh codec.

[0096] One or more (or all) of the following features may be implemented in this embodiment:• The V3C occupancy component (V3C unit type V3C_OVD) is ignored.• V3C_AVD is used to code texture attribute information.• V3C_GVD is used to code displacement information.• When coded with video, the V-DMC displacement is available in the V3C units of type V3C_GVD (geometry) but may or may not follow the definition of “Geometry” used in V3C. For instance, the displacement may be coded losslessly, in mono, and / or with a different bit depth. o The information stored in a sub-bitstream of a V3C unit of type V3C_GVD in V-DMC is related to the displacement coefficient for sub-divided vertices.• Some of the video decoders may have the capabilities to decode bitstreams with the chroma format 4:4:4, such as HEVC444. o Typically, chroma format 4:2:0 is widely deployed in the market in hardware- accelerated video decoders.• The ptl_codec_group_idc is specified for V-DMC texture and V-DMC displacement.• The use of MPEG basemesh codec may be made mandatory in such embodiments. o Any other basemesh codec cannot be used. o CCM SEI message does not describe codec mapping for basemesh codec.(§ 1.2.2) Default Basemesh in Profile Codec Group

[0097] In embodiments described in the previous section, the use of any other basemesh codec specified in MPEG or elsewhere is restricted. The intention to refer to any basemeshcodec exists in the current working draft of ISO / IEC 23090-29, in which the basemesh codec is identified with a codec ID. The syntax element vps_ext_bmesh_data_substream_codec_id indicates the identifier of the codec used to compress the basemesh data for an atlas. This codec may be identified through the profiles a component codec mapping SEI message, orthrough means specified outside ISO / IEC 23090- 5 and ISO / IEC 23090-29 specification.

[0098] Example embodiments include a basemesh codec sub-component in the V-DMC profile codec group is desirable. In Table 6, the profile codec group corresponding to a ptl_profile_codec_group_idc value in the range 5 to 14 indicates that the MPEG basemesh codec (Annex H : Basemesh codec in ISO / IEC 23090-29) is the default basemesh codec for encoding the basemesh data in the V-DMC bitstream. There is a provision to refer to any other basemesh codec using ptl_profile_codec_group_idc value 127. A Component Codec Mapping (CCM) SEI message is be present and indicates a mapping to a stream format of a basemesh codec to vps_ext_bmesh_data_substream_codec_id. By exposing the basemesh codec, it provides the flexibility to refer to future versions or different basemesh codecs than the one specified in Annex H.

[0099] A 4CC code for MPEG basemesh codec may be used to indicate that the basemesh information in the V-DMC conforms to the stream format of the MPEG basemesh codec.

[0100] In combination with some or all features of embodiments described in section 1.2.1 , above, some embodiments further include one or more (or all) of the following features:• Inclusion of MPEG basemesh codec in profile codec group component.• Flexibility to refer to any other basemesh codec specified in MPEG or elsewhere using the CCM SEI.• Basemesh decoder may be profiled based on bit-depth requirement. o Different basemesh decoders may have different capabilities on bit-depth to decode the basemesh bitstream.• When coded with video, the VDMC displacement is available in the V3C_GVD V3C unit type (Geometry) but may or may not follow the definition of “Geometry” in V3C. For instance, it may be coded losslessly, in mono, with a different bitdepth.

[0101] For ptl_profile_codec_group_idc equal to 5, 6, 7, 8 and 9, all video sub-bitstreams, i.e., displacement and texture attribute sub-bitstreams, conform to the stream format identified by their respective 4CC codes.

[0102] For ptl_profile_codec_group_idc equal to 10, 11 , 12,13, and 14, the texture attribute video sub-bitstream conform to the stream format identified by the respective 4CC codes. The displacement sub-bitstream conforms to the stream format identified by Annex J in ISO / IEC 23090-29or a 4CC code registered for Annex J in ISO / IEC 23090-29.

[0103] For ptl_profile_codec_group_idc equal to 5, 6, 7, 8, 9, 10, 11 , 12, 13 , 14, the basemesh sub-bitstream conforms to the stream format identified by Annex H in ISO / IEC 23090-29 or a 4CC code registered for Annex H in ISO / IEC 23090-29.Table 5. Profile codec group component for VDMC with default MPEG basemesh codec. (§ 1.2.3) Intra and inter mesh for MPEG basemesh codec in profile codec group

[0104] One of the limitations of the embodiment in Section 1.2.2 is that a basemesh codec may employ different codecs to code static mesh and motion data (which may be referred to as the intra and inter mesh codec, respectively). There may be different methods to exposeand profile the intra and inter mesh codecs in the bitstream. Example embodiments in this section may demonstrate one or more (or all) of the following features:• Inter and intra mesh codecs are incorporated in the profile codec group at V3C level.• Use of the MPEG basemesh codec is mandatory.• Intra and inter mesh codecs within the basemesh codec are described with their appropriate stream format identifiers.• The static mesh decoder and motion decoder may be profiled based on different bitdepth requirements.

[0105] Table A-1 in ISO / IEC 23090-5 is extended to support different codecs for displacement and texture components of a V-DMC bitstream as well as static mesh codec and motion codec for the basemesh bitstream as shown in Table 7. The profile codec groups for ptl_profile_codec_group_idc in the value range 5 to 14 assume that the MPEG basemesh codec is the mandatory codec to code the basemesh data in the V-DMC bitstream. Use of the CCM SEI message to change the basemesh codec to any other basemesh codec is restricted.

[0106] Expressing the inter and intra mesh codecs allows codec requirements to be examined at the V3C level rather than basemesh level. Early identification of intra and inter mesh codec information may be useful in appropriate stream selection and initiating relevant decoders. A V-DMC-based decoder may read the information about the intra and inter mesh codecs at the V3C level to identify the capabilities used to decode the basemesh bitstream.

[0107] For ptl_profile_codec_group_idc equal to 5, 6, 7, 8 and 9, all video sub-bitstream, i.e., displacement and texture attribute sub-bitstreams, conform to the stream format identified by their respective 4CC codes.

[0108] For ptl_profile_codec_group_idc equal to 10, 11 , 12,13, and 14, the texture attribute video sub-bitstream conform to the stream format identified by the respective 4CC codes. The displacement sub-bitstream conforms to the stream format identified by Annex J in ISO / IEC 23090-29 or a 4CC code registered for Annex J in ISO / IEC 23090-29.

[0109] For ptl_profile_codec_group_idc equal to 5, 6, 7, 8, 9, 10, 11 , 12, 13 ,14, the static mesh codec in the basemesh sub-bitstream and the motion codec in the basemesh subbitstream conforms to the stream format identified by Annex I in ISO / IEC 23090-29 and Annex H in ISO / IEC 23090-29 respectively. In the future, it is expected that 4CC codes for the static mesh codec and the motion codec will be registered. In which case, the registered 4CC codes for the static mesh codec in Annex J and 4CC code for the motion codec in Annex H will be used.Table 6. Profile codec group component for VDMC with inter and intra mesh codec and mandatory MPEG basemesh codec.

[0110] Currently, the V-DMC specification defines a single Basemesh codec composed of a generic HLS framework (Annex H) and a motion codec (Annex H) that reference a static mesh codec (Annex I). The motion codec and / or static mesh codec could evolve over time and may have new profiles. Instead of pointing to Annex I and H in the above table, various 4CC values could be used for each of them. The same principle would apply to Annex J.(§ 1.2.4) Full Exposure of Codecs in Profile Codec Group

[0111] One limitation of example embodiments described in Section 1.2.3, is the use of theMPEG basemesh codec to code the basemesh information. This limits the flexibility of usingany other basemesh codec which may be a more efficient codec to code basemesh information.

[0112] This section describes an example method to expose different codecs involved in order to decode a V-DMC bitstream. Table 8 describes the codec groups with different combinations of codecs used to decode sub-components, i.e., displacement, texture, and basemesh, as well as basemesh sub-components i.e., static mesh and motion data. Table 8 provides the following:• Functionalities for different sub-components such as displacement, texture, static mesh, and motion decoder as defined in Section 1 .2.3 holds in this section as well. • The basemesh is incorporated as one of the components in the profile codec group component of V-DMC• The MPEG basemesh codec is described as the default basemesh codec for all the profiles defined in this section.• Intra and inter mesh codec within the basemesh codec are described with their appropriate stream format identifiers.• The static mesh decoder and motion decoder may be profiled based on different bitdepth requirements.Table 7. Profile codec group component for VDMC with full expose of different codecs involved.

[0113] In another embodiment, Table 8 extends Table A1 in ISO / IEC 23090-5. Table 8 fully exposes the different codecs for displacement and texture components of a V-DMC bitstream as well as the static mesh codec and motion codec for the basemesh bitstream. Exposure of all the different decoders, e.g., displacement, texture attribute, basemesh, inter mesh, and intra mesh decoders at the V3C level will allow absolute flexibility for a V-DMC bitstream to express the required decoding capabilities for its sub-components.

[0114] The profile codec group for ptl_profile_codec_group_idc values in the range 5 to 14 indicate that the MPEG basemesh codec is the default basemesh codec to codec basemesh data in the V-DMC bitstream for all the profiles. As described in previous sections, the displacement information may be coded using video codec or arithmetic codecs. Therefore, different decoders for decoding the displacement sub-bitstream are described in Table 8.

[0115] The texture sub-components are purely video-based information. Therefore, video decoders are used to decode the texture attribute sub-component.

[0116] The intra and inter mesh codec are exposed at the V3C level.

[0117] Similarly, there is a benefit to define codecs for static mesh and motion data separately which may be specified in MPEG or outside of MPEG.

[0118] For ptl_profile_codec_group_idc equal to 5, 6, 7, 8 and 9, all of the video subbitstreams, i.e., displacement and texture attribute sub-bitstreams, conform to the stream format identified by their respective 4CC codes.

[0119] For ptl_profile_codec_group_idc equal to 10, 11 , 12, 13, and 14, the texture attribute video sub-bitstream conform to the stream format identified by the respective 4CC codes. The displacement sub-bitstream conforms to the stream format identified by Annex J in ISO / IEC 23090-29. In future, there is an expectation that a 4CC code for Annex J in ISO / IEC 23090- 29 will be registered. The registered 4CC for Annex J would then be used to indicate the codec for AC-based displacement bitstream.

[0120] For ptl_profile_codec_group_idc equal to 5, 6, 7, 8, 9, 10, 11 , 12, 13, and 14, the basemesh sub-bitstream conforms to the stream format identified by the Annex H in ISO / IEC 23090-29.

[0121] For ptl_profile_codec_group_idc equal to 5, 6, 7, 8, 9, 10, 11 , 12, 13, and 14, the static mesh codec in the basemesh sub-bitstream and motion codec in the basemesh sub-bitstream conforms to the stream format identified by Annex I in ISO / IEC 23090-29 and Annex H in ISO / IEC 23090-29 respectively.(§ 1.3) Extending Reconstruction Component for V-DMC

[0122] A table, e.g., Table 8 defines the profile reconstruction component for a V-DMC bitstream. Table 8 may provide a list of defined reconstruction profile components for V-DMC and of the allowed values for the syntax element ptl_profile_reconstruction_idc, for example values in the range 251-254.Table 8. Reconstruction profile components for V-DMC.(§ 1.4) Indicating Displacement and Basemesh codecs in the V-DMC extensionExample embodiments provide a way to keep the V3C geometry information for V-DMC displacement. Some such embodiments have one or more (or all) of the following features:• A V3C component other than Geometry remains as defined in V3C.• When coded with video, the V-DMC displacement is available in the V3C_GVD V3C unit type (Geometry) but may or may not follow the definition of “Geometry” in V3C. For instance, it may be coded losslessly, in mono, and / or with a different bit depth as per the embodiments in Section 1.2 of the present disclosure. Other aspects defined in V3C for V3C_GVD may still apply.

[0123] As described above, the displacement sub-component may not fit the requirements of geometry video in ISO / IEC 23090-5. Fundamentally, the information stored in geometry components of V3C is depth information. However, in the case of displacement, the information stored relates to displacement coefficients. Therefore, it may be desirable to represent the displacement sub-components as a separate sub-component within V3C.

[0124] In the case where the displacement sub-component is coded using a video codec, some of the aspects of decoding and format conversion of geometry video may still apply. In this case, the use of V3C_GVD is justified for video-based displacement information.

[0125] In Section 1 , above, a new V3C unit type V3C_DPD is introduced. V3C_DPD may be used to indicate an arithmetically coded displacement bitstream. Such a codec is not video based. The use of V3C_DPD is a clear differentiator that an AC codec will be employed to decode the payload for the V3C_DPD V3C unit type.

[0126] In some embodiments, a new syntax element vps_ext_displacement_data_substream_codec_id[j] is introduced in the V-DMC VPS extension. A vps_ext_displacment_data_substream_codec_id[j] specifies the codec identifiers for the displacement bitstream for atlas with atlas ID j. The vps_ext_displacment_data_substream_codec_id may be mapped to a video-based displacement decoder or an AC-based displacement decoder. When present, the gi_geometry_codec_id[ atlasID ] is ignored.

[0127] The V3C parameter set V-DMC extension syntax table, defined in ISO / IEC 23090-29, may be extended as follows with the addition of vps_ext_displacement _data_substream_codec_id[j], as indicated by a dagger (t):

[0128] As described above, rather than using the V3C_GVD V3C unit type for an arithmetically coded displacement sub-bitstream, a new V3C unit type, e.g., V3C_DPD may be created. In that case, the V3C VPS parameter set vps_geometry_video_present_flag[ j ] is set to zero or ignored when a V-MDC profile is identified, and the vps_ext_ ext_displacement _data_substream_codec_id[j] is used to identify either a video codec or an AC codec for the displacement bitstream.

[0129] The displacement_information() syntax element structure is read when a displacement bitstream is present, i.e., vps_ext_displacment_present_flag is set to 1. The displacementJnformationO syntax element structure provides syntax elements to describe the syntax element for the displacement bitstream. The details on the syntax element are described in the subsequent syntax table. The V-DMC VPS extension table may be modified as follows, with the addition of the elements indicated by a dagger (t).

[0130] The displacementjnformation may provide information such as bit-depth, codec ID, 2D bit depth in case of nominal conversion of a 2D video bitstream, 3D bit depth for nominal 3D displacement coefficients, for example as follows:

[0131] In some embodiments, the semantics of the syntax elements shown above are as follows.• dp_displacment_codec_id specifies the mapping index of a codec identifier of the video decoder or ac decoder used to decode the displacement subbitstream, if present, forthe atlas with atlas ID j, dp_displacement_codec_id[ j ] is in the range of 0 to 255, inclusive.• dp_displacement_2d_bit_depth_minus11 indicates the nominal 2D bit depth to which displacement video for atlas ID j is converted to. dp_displacement_2d_bit_depth_minus1 [ j ] is in the range of 0 to 31 , inclusive.• dp_displacement_msb_align_flag indicates how the decoded displacement video samples associated with an atlas are converted to samples at the nominal displacement bit depth.• dp_displacement_3d_bit_depth_minus1 plus 1 indicates the bit depth of the 3D displacement coefficients of the reconstructed mesh content for an atlas.• dp_reserved_zero_5bits is equal to zero in this bitstream. This element is added to ensure byte alignment. This syntax element may not be used if byte alignment through adding more syntax element in the displacementJnformationO structure.(§ 1.5) Defining Profile in V-DMC VPS Extension, or Defining a VDMC Profile Tier Level Syntax / Semantic

[0132] In some embodiments, as an alternative to features described in section 1.2, profile, tier, and level syntax (and corresponding semantic) are considered for attribute subcomponents in V-DMC. In such embodiments, the V3C PTL does not provide information about basemesh and displacement sub-components of a VDMC bitstream. Instead, a new VDMC specific profile tier level syntax is defined in the VPS extension for VDMC. For example, the following may be defined in ISO / IEC 23090-29, with the syntax element vdmc_profile_tier_level( ) being added:

[0133] In some embodiments, a syntax element such as “vmdc_profile_present_flag” may be indicated in the PTL at V3C to signal that profile information for the geometry is to be retrieved from the V-DMC extension, as shown here:

[0134] In an example embodiment, the vmdc_profile_present_flag value of zero indicates that profiling information for the basemesh and displacement along with attribute subcomponent is present in the PTL at V3C level. The profile components as described in Sections 1.1 , 1.2, and 1.3, above, may then be applied as is. A vdmc_profile_present_flag value of 1 may specify that the profiling information for the geometry information, e.g. the basemesh and displacement bitstream, is present in the PTL structure specified within VDMC VPS extension as described in the paragraph below. The profile information for attributes may be defined as is at the VPS level.

[0135] The profile tier level (PTL) syntax for non-attribute sub-components, such as basemesh and displacement sub-components, is described in a VDMC specific PTL structure. A PTL syntax element in such a way disassociates the decoding and reconstruction processof basemesh and displacement from the attribute reconstruction. This means that basemesh and displacement decoding and reconstruction will result in a geometry representation of the dynamic mesh content with no texture information. In some applications, this may be called for as shown in Section 1.1 for the VDMC geometry only profile.

[0136] In an example, the syntax elements in a vdmc_profile_tier_level() structure describe the profiling information for geometrical sub-components, namely basemesh and displacement sub-components. The data structure may be configured as follows.

[0137] The syntax element ptl_vdmc_profile_codec_group_idc may be defined in accordance with embodiments in Section 1.2, above, for basemesh and displacement subcomponents.

[0138] The syntax element ptl_vdmc_profile_toolset_idc may be defined in accordance with embodiments in Section 1.1 , above for basemesh and displacement sub-components.

[0139] The syntax element ptl_vdmc_profile_reconstruction_idc may be defined in accordance with embodiments in Section 1.3, above, for basemesh and displacement subcomponents.

[0140] Along with profiling information, in some embodiments, an additional syntax element may also be defined. For example, as supported in video specifications such as HEVC, and others, level and tier describe a set of limits on the on the values that may be taken by the syntax elements of the video specification. The same set of tier and level definitions is used with all profiles. However, individual implementations may support a different tier and within a tier a different level for each supported profile. For any given profile, a level of a tier corresponds to a particular decoder processing load and memory capability.

[0141] ptl_vdmc_tier_flag specifies the tier context for the interpretation of ptl_vdmc_level_idc as specified in Annex A. ptl_vdmc_tier_flag may be used to determine different processing loads for a level of a conformant VDMC bitstream. ptl_vmdc_level_idc indicates a level to which the VDMC bitstream conforms. This may be specified as specifiedin Annex A of ISO / IEC 23090-29. Bitstreams may not contain values of ptl_vdmc_level_idc other than those specified in Annex A.(§ 2) MPEG Basemesh Profile

[0142] One feature of embodiments as described in Section 1.2.3 and Section 1.2.4 is a high level of exposure of the MPEG basemesh codec internal codecs and its functioning to the 3C level. This may be disadvantageous in some implementations.

[0143] In some alternative embodiments, the design of the V-DMC framework may be such that the internal workings of the basemesh codec are abstracted from V3C. For example, the MPEG basemesh codec in Annex H of ISO / IEC 23090-29 employs two separate codecs which are referred as the intra mesh codec and the inter mesh codec. The intra mesh codec is responsible for compression of a static mesh and the inter mesh codec is responsible for temporal compression of mesh topology. The internal compression of the basemesh may not be exposed to V3C. The use or restriction of the basemesh toolset may be defined in the local scope of basemesh codec rather the global scope of 3C.

[0144] Some embodiments specify a profiling mechanism for the MPEG basemesh codec as well.

[0145] Currently, there are three syntax elements in Annex H clause H.8.1.3.1.3. of ISO / IEC 23090-29, namely bmptl_profile_codec_idc, bmptl_profile_toolset_idc, and bmptl_profile_reconstruction_idc, that describe the codec group profile component, toolset profile component and reconstruction profile component for a MPEG basemesh bitstream respectively.

[0146] The syntax elements are used to describe different profiles for the MPEG basemesh codec bitstream. A codec group profile may describe the sub-codecs combinations such as the intra mesh codec defined in Annex J and inter mesh codec defined in Annex H. A toolset profile for a basemesh may describe a set of functionalities which specifies a subset of algorithmic features and limits that are supported by a basemesh decoder conforming to that profile. A reconstruction profile for the MPEG basemesh may describe the pre-reconstruction, reconstruction, post-reconstruction, and adaptation tools supported or recommended to achieve conformance in terms of 3D reconstruction. A basemesh decoder may support and may be able to conform to multiple reconstructions. When an MPEG decoder claims to be operating at a particular conformance point B, it is capable of reconstructing a mesh frame according to the reconstruction recommendations specified by that profile.(§ 2.1) MPEG basemesh codec group profile

[0147] Currently, the MPEG basemesh codec employs two codecs to code basemesh information. Since the current V-DMC specification in defines a static mesh codec, there is one value for bmptl_profile_codec_group_idc, i.e., value 0 identified. A basemesh bitstream with bmptl_profile_codec_group_idc value 0 conform to the stream format of the Annex I for the intra mesh data and conforms to the stream format of inter mesh data, i.e., Annex H Clause 8.1.3.9. It is expected that 4CC code for the intra mesh codec in Annex I will be registered in the future. In which case, the 4CC code of the intra mesh codec will replace the reference to “Annex I” in Table 9. Similarly, it is expected that a 4CC may be registered for inter mesh codec. The 4CC code of the inter mesh codec will replace the reference to “Annex H” in Table 9.

[0148] Currently, the semantics of bmptl_profile_codec_group_idc has a reference to undefined Annex in V-DMC. A new Annex or a new clause in Annex H in ISO / IEC 23090-29 may be added to define codec group profile components.

[0149] Such an annex may provide information about the codec group profile component for MPEG basemesh as shown in Table 9.Table 9. Codec group profile component for basemesh codec.

[0150] A tick mark (7) in Table 10, below, indicates that a particular feature is supported by the defined profile. A dash symbol, i.e.indicates that support of a particular feature is specified by means outside this document.

[0151] In example embodiments, all sub-bitstreams of a basemesh bitstream conform to the stream format indicated in the component codec mapping SEI (F.2.11 in ISO / IEC 23090-5).

[0152] For bmptl_profile_codec_group_idc equal to 0, the intra mesh sub-bitstream conforms to the stream format identified by the Annex I or the 4CC code defined for Annex I static mesh codec, and the inter mesh sub-bitstream conform to the stream format identified by the Annex H clause H.8.1.3.9 or the 4CC code defined for Annex H inter mesh data unit syntax. The component codec mapping SEI message (in F.2.11 in ISO / IEC 23090-5[1]), when present,the ccm_codec_mappings_count_minus1 has value 1 , and instances ] of ccm_codec_4CC[j] indicate the value of 4CC codes for the inter mesh codec and intra mesh codec respectively.Table 10. Basemesh Codec group profile component supported functionality.(§ 2.2) MPEG Basemesh Toolset Profile

[0153] Currently, the semantics of bmptl_profile_codec_group_idc has a reference to an undefined V-DMC Annex. A new Annex may be described or a new clause in Annex H in ISO / IEC 23090-29 may be described to define codec group profile components.

[0154] The new annex provides information about the codec group profile component for theMPEG basemesh as shown in Table 11. Table 11 provides a list of defined toolset profile components for the MPEG basemesh and their corresponding identifying syntax element values, e.g. bmptl_profile_toolset_idc and bmptc_one_mesh_frame_only flag.Table 11. Profile toolset component for basemesh codec.

[0155] MPEG basemesh toolset profile components indicating the Basemesh Basic(bmptl_profile_toolset_idc = 0), Basemesh Simple still (bmptl_profile_toolset_idc = 0 andbmptc_one_mesh_frame_only_flag = 1 ) conform to the syntax element restriction specified in Table 12. If a syntax element is not mentioned in Table 12 it is not restricted through a toolset profile component.

[0156] In the Basemesh Simple and Basemesh Simple Still profiles, a common set of syntax element restrictions may apply. In the current context of V-DMC, at most two basemesh attributes may be called for. These attributes are identified by attribute type as ATTR_TEXCOORD, and ATTR_FACEGROUP_ID. Texture coordinates, such as, ATTR_TEXCOORD, are used to map texture attribute onto the 3D geometry. The Facegroup ID attribute, attribute type ATTR_FACEGROUP_ID, is used to map mesh faces to sub- patches. The Basemesh Simple and Basemesh Simple Still profile does not have any extension to the basemesh sequence parameter set and the basemesh frame parameter set. Submeshes for each mesh frame are specified using a submesh ID.Table 12. Allowed syntax element values for MPEG Basemesh toolset profile components.

[0157] In the context of V-DMC, when MPEG basemesh is used to code the basemesh subcomponent, then bmptl_profile_toolset_idc may be equivalently matched with a ptl_profile_toolset_idc in the V3C specification for V-DMC (as specified in Section 1.1 , above). This ensures that correct profile toolsets are chosen when the MPEG basemesh bitstream isused in a V-DMC context. Without a correct profile toolset correspondence, the V-DMC decoder will be ill informed about the characteristics of the bitstream and the VDMC decoder may not be able to instantiate the proper toolset used for decoding the V-DMC bitstream.

[0158] For example, Basemesh Simple profile can be used with V-DMC Basic, V-DMC Basic with arithmetic codec for displacement, V-DMC basic packed, V-DMC Geometry profiles as specified in Section 1.1 , above, basemesh static profile can only be used with V-DMC Basic Still, V-DMC basic with arithmetic codec for displacement, V-DMC basic packed still, and V- DMC Static Geometry. The toolset profile of a basemesh codec should be matched with toolset profile of a V-DMC codec.(§ 2.3) MPEG Basemesh Reconstruction Profile

[0159] A MPEG basemesh reconstruction profile component can be identified by bmptl_profile_reconstruction_idc syntax element. Currently, bmptl_profile_reconstruction_idc has a reference to an undefined Annex. A new Annex may be described or a new clause in Annex H in ISO / IEC 23090-29 may be described to define reconstruction profile components.

[0160] The new annex will provide a list of defined reconstruction profile components for basemesh and of the allowed values for syntax element bmptl_profile_reconstruction_idc as shown in the table below.(§ 3) Association of Atlas with Basemesh Bitstream

[0161] A V-DMC may contain multiple atlases. Each atlas corresponds to a basemesh subbitstream. In the V3C parameter set extension for V-DMC, the assumption is that each atlas has an atlasID which is equal to the index of the atlas in the range 0 to vps_atlas_count_minus1 . However, this assumption is false as atlasID may not always be equal to the atlas index. Therefore, an additional processing is implemented in some embodiments as shown in the syntax below. Rows of the syntax marked with proposed revisions are marked with a dagger (t).

[0162] According to this syntax, an atlas ID for each atlas bitstream is retrieved using the vps_atlas_id array. The vps_atlas_id array is indexed to retrieve the corresponding atlasID to describe the association with the basemesh bitstream. This enables a similar mechanism of atlas bitstream associated as performed for other sub-components such as attributes.

[0163] Without this processing, there is an implied assumption that the atlasID for an atlas is the same as its index in the atlas array in the range 0 to vps_atlas_count_minus1. This scenario is limiting and may lead to inconsistency. The flexibility to arbitrarily choose a value for an atlasID is lost when the index is used as an atlas. For example, the content author may want to associate an atlas with an atlasID: 1 in a V3C bitstream with only one atlas bitstream. In case of the index of the atlas is used for atlasID, the atlasID associated with the atlas bitstream would be 0. This contradicts the content author indent. The content author loses control over the description of the atlas.

[0164] Moreover, the specification ISO / IEC 23090-5 and its derived specification use the concept of an explicit atlasID specifies the ID of the atlas that corresponds to the current V3C unit. Every V3C unit header specifies the ID of the atlas that corresponds to the current V3C unit with syntax element vuh_atlas_id.

[0165] An encoding method in accordance with this section may include encoding a first parameter set of a volumetric video bitstream, such as the parameter set v3c_parameter_set, by iterating through one or more indices associated with respective atlases. For each index, an associated atlas identifier of the respective atlas, such as vps_atlas_id, is encoded. A second parameter set, such as vps_vdmc_extension, is encoded to provide information for one or more sub-bitstreams of the volumetric video bitstream. To encode the second atlas, a second iteration is performed through the indices. For each index in the second iteration, the associated alas identifier is determined, and a plurality of parameters for the atlas identifiedby the associated atlas identifier are encoded. An encoding apparatus according to some embodiments comprises one or more processors configured to perform such a method.

[0166] A decoding method in accordance with this section may include decoding a first parameter set of a volumetric video bitstream, such as the parameter set v3c_parameter_set, by iterating through one or more indices associated with respective atlases. For each index, an associated atlas identifier of the respective atlas, such as vps_atlas_id, is decoded. A second parameter set, such as vps_vdmc_extension, is decoded to provide information for one or more sub-bitstreams of the volumetric video bitstream. To decode the second atlas, a second iteration is performed through the indices. For each index in the second iteration, the associated alas identifier is determined, and a plurality of parameters for the atlas identified by the associated atlas identifier are decoded. A decoding apparatus according to some embodiments comprises one or more processors configured to perform such a method.

[0167] A parameter such as vps_atlas_count_minus1 indicating a number of atlases in the volumetric video bitstream is coded in the first parameter set. The number of iterations performed in the first and the second iterations may be determined by the indicated number. For example, the number of iterations may be vps_atlas_count_minus1+1.Example Decoder

[0168] FIG. 7 is a functional block diagram of an example decoder according to some embodiments. For the sake of clarity, not all features and configurations disclosed herein are expressed graphically in FIG. 7. The decoder of FIG. 7 receives a bitstream, which may be a V3C bitstream, and demultiplexes it into component sub-bitstreams. Profile information may also be parsed from the bitstream, e.g. at the V3C level. The profile information may be used to indicate a decoder configuration. This profile information allows the decoder to instantiate tools as appropriate for the particular bitstream. For example, the profile information may indicate which basemesh codec is to be used to decode the basemesh, and the decoder is configured accordingly to direct the basemesh sub-bitstream to the appropriate decoder module. The profile information may indicate whether the displacement sub-bitstream is to be decoded using an arithmetic decoder or a video decoder (and if it is a video decoder, which video decoder), and the decoder is configured accordingly to direct the displacement subbitstream to the appropriate decoder module. The profile information may indicate which video decoder is to be used to code the texture sub-bitstream, and the decoder is configured accordingly to direct the displacement sub-bitstream to the appropriate decoder module. The profile information may include further information, such as bit depth information, that may be used to configure the individual decoder modules. The deformed mesh may be reconstructed from the basemesh and the displacements, and the reconstructed deformed mesh, togetherwith the reconstructed texture, may be rendered or otherwise processed according to known techniques.Further Embodiments

[0169] An encoding method according to some embodiments comprises: encoding a first parameter set of a volumetric video bitstream, including performing a first iteration through one or more indices associated with respective atlases and, for each index in the first iteration, encoding an associated atlas identifier of the respective atlas; and encoding a second parameter set for one or more sub-bitstreams of the volumetric video bitstream including performing a second iteration through the one or more indices, and for each index in the second iteration, determining the associated alas identifier and encoding a plurality of parameters for the atlas identified by the associated atlas identifier. An encoding apparatus according to some embodiments comprises one or more processors configured to perform such a method.

[0170] A decoding method according to some embodiments comprises: decoding a first parameter set of a volumetric video bitstream, including performing a first iteration through one or more indices associated with respective atlases and, for each index in the first iteration, decoding an associated atlas identifier of the respective atlas; and decoding a second parameter set for one or more sub-bitstreams of the volumetric video bitstream including performing a second iteration through the one or more indices, and for each index in the second iteration, determining the associated alas identifier and decoding a plurality of parameters for the atlas identified by the associated atlas identifier.

[0171] In some embodiments, a parameter indicating a number of atlases in the volumetric video bitstream is coded in the first parameter set, and the number of iterations performed in the first and the second iterations is determined by the indicated number.

[0172] In some embodiments, the first parameter set is a V3C parameter set.

[0173] In some embodiments, the second parameter set is a video parameter set, VPS, extension for video-based dynamic mesh coding, VDMC.

[0174] In some embodiments, the plurality of parameters include a codec identifier of the respective atlas.

[0175] In some embodiments, the plurality of parameters include a frame width and a frame height of the respective atlas.

[0176] A method according to some embodiments comprises: obtaining a volumetric video bitstream, wherein the volumetric video bitstream includes at least one sub-bitstream, and wherein the volumetric video bitstream further includes a parameter set that provides profileinformation for the at least one sub-bitstream; based on the profile information, selecting a decoder configuration for decoding the at least one sub-bitstream; and decoding the at least one sub-bitstream using the selected decoder configuration. In some embodiments, the volumetric video bitstream is a V3C bitstream, and wherein the parameter set is provided at the V3C level.

[0177] In some embodiments, at least one of the sub-bitstreams is a basemesh bitstream, and wherein the parameter set includes information indicating whether the basemesh bitstream encodes a static mesh or a dynamic mesh.

[0178] In some embodiments, the sub-bitstreams include a static mesh bitstream and a displacement bitstream, and the profile information indicates whether the displacement bitstream is coded using an arithmetic codec.

[0179] In some embodiments, the profile information includes information identifying a video codec to be used for decoding at least one of the sub-bitstreams.

[0180] Some embodiments include a flag signaled at the bitstream level, wherein the flag indicates whether the information identifying the video codec is signaled at the bitstream level or at a sub-bitstream level.

[0181] In some embodiments, the sub-bitstreams include at least a displacement bitstream and a texture attribute bitstream, and wherein the profile information identifies at least a first codec to be used for decoding the displacement bitstream and a second codec to be used for decoding the texture attribute bitstream.

[0182] In some embodiments, the information identifying the first codec and the second codec is an integer value.

[0183] In some embodiments, the first codec and the second codec are the same video codec. In other embodiments, the first codec is an arithmetic codec and the second codec is a video codec.

[0184] In some embodiments, the sub-bitstreams include a displacement bitstream, wherein the parameter set includes a video parameter set extension, and wherein the video parameter set extension identifies a codec to be used for decoding the displacement bitstream.

[0185] An apparatus according to some embodiments comprises one or more processors, the apparatus being configured to perform any of the methods described herein.

[0186] An apparatus according to some embodiments comprises at least one processor and a computer-readable medium storing instructions for performing any of the methods described herein.

[0187] A computer-readable medium according to some embodiments stores instructions for performing any of the methods described herein.

[0188] A signal according to some embodiments comprises a volumetric video bitstream, wherein the volumetric video bitstream includes at least one sub-bitstream, and wherein the volumetric video bitstream further includes a parameter set that provides profile information for the at least one sub-bitstream.

[0189] A method according to some embodiments comprising encoding in a signal any of the information, e.g. profile information, described herein.

[0190] Some embodiments include a computer-readable medium storing any of the information described herein.

[0191] To the extent the present disclosure may describe some features as mandatory, needed, or required, or uses similar language, it should be understood that such features are only being described as mandatory, needed, or required according to the syntax of a particular embodiment. Such features are not necessarily mandatory, needed, or required, or even used at all, in other embodiments.

[0192] This disclosure describes a variety of aspects, including tools, features, embodiments, models, approaches, etc. Many of these aspects are described with specificity and, at least to show the individual characteristics, are often described in a manner that may sound limiting. However, this is for purposes of clarity in description, and does not limit the disclosure or scope of those aspects. Indeed, all of the different aspects can be combined and interchanged to provide further aspects. Moreover, the aspects can be combined and interchanged with aspects described in earlier filings as well.

[0193] The aspects described and contemplated in this disclosure can be implemented in many different forms. While some embodiments are illustrated specifically, other embodiments are contemplated, and the discussion of particular embodiments does not limit the breadth of the implementations. At least one of the aspects generally relates to encoding and decoding, and at least one other aspect generally relates to transmitting a bitstream generated or encoded. These and other aspects can be implemented as a method, an apparatus, a computer readable storage medium having stored thereon instructions for encoding or decoding XR content data according to any of the methods described, and / or a computer readable storage medium having stored thereon a bitstream generated according to any of the methods described.

[0194] Various methods are described herein, and each of the methods comprises one or more steps or actions for achieving the described method. Unless a specific order of steps oractions is required for proper operation of the method, the order and / or use of specific steps and / or actions may be modified or combined. Additionally, terms such as “first”, “second”, etc. may be used in various embodiments to modify an element, component, step, operation, etc., such as, for example, a “first decoding” and a “second decoding”. Use of such terms does not imply an ordering to the modified operations unless specifically required. So, in this example, the first decoding need not be performed before the second decoding, and may occur, for example, before, during, or in an overlapping time period with the second decoding.

[0195] Various numeric values may be used in the present disclosure, for example. The specific values are for example purposes and the aspects described are not limited to these specific values.

[0196] Embodiments described herein may be carried out by computer software implemented by a processor or other hardware, or by a combination of hardware and software. As a nonlimiting example, the embodiments can be implemented by one or more integrated circuits. The processor can be of any type appropriate to the technical environment and can encompass one or more of microprocessors, general purpose computers, special purpose computers, and processors based on a multi-core architecture, as non-limiting examples.

[0197] When a figure is presented as a flow diagram, it should be understood that it also provides a block diagram of a corresponding apparatus. Similarly, when a figure is presented as a block diagram, it should be understood that it also provides a flow diagram of a corresponding method / process.

[0198] The implementations and aspects described herein can be implemented in, for example, a method or a process, an apparatus, a software program, a data stream, or a signal. Even if only discussed in the context of a single form of implementation (for example, discussed only as a method), the implementation of features discussed can also be implemented in other forms (for example, an apparatus or program). An apparatus can be implemented in, for example, appropriate hardware, software, and firmware. The methods can be implemented in, for example, a processor, which refers to processing devices in general, including, for example, a computer, a microprocessor, an integrated circuit, ora programmable logic device. Processors also include communication devices, such as, for example, computers, cell phones, portable / personal digital assistants (“PDAs”), and other devices that facilitate communication of information between end-users.

[0199] Reference to “one embodiment” or “an embodiment” or “one implementation” or “an implementation”, as well as other variations thereof, means that a particular feature, structure, characteristic, and so forth described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrase “in one embodiment” or “in anembodiment” or “in one implementation” or “in an implementation”, as well any other variations, appearing in various places throughout this disclosure are not necessarily all referring to the same embodiment.

[0200] Additionally, this disclosure may refer to “determining” various pieces of information. Determining the information can include one or more of, for example, estimating the information, calculating the information, predicting the information, or retrieving the information from memory.

[0201] Further, this disclosure may refer to “accessing” various pieces of information. Accessing the information can include one or more of, for example, receiving the information, retrieving the information (for example, from memory), storing the information, moving the information, copying the information, calculating the information, determining the information, predicting the information, or estimating the information.

[0202] Additionally, this disclosure may refer to “receiving” various pieces of information. Receiving is, as with “accessing”, intended to be a broad term. Receiving the information can include one or more of, for example, accessing the information, or retrieving the information (for example, from memory). Further, “receiving” is typically involved, in one way or another, during operations such as, for example, storing the information, processing the information, transmitting the information, moving the information, copying the information, erasing the information, calculating the information, determining the information, predicting the information, or estimating the information.

[0203] It is to be appreciated that the use of any of the following 7”, “and / or”, and “at least one of’, for example, in the cases of “A / B”, “A and / or B” and “at least one of A and B”, is intended to encompass the selection of the first listed option (A) only, or the selection of the second listed option (B) only, or the selection of both options (A and B). As a further example, in the cases of “A, B, and / or C” and “at least one of A, B, and C”, such phrasing is intended to encompass the selection of the first listed option (A) only, or the selection of the second listed option (B) only, or the selection of the third listed option (C) only, or the selection of the first and the second listed options (A and B) only, or the selection of the first and third listed options (A and C) only, or the selection of the second and third listed options (B and C) only, or the selection of all three options (A and B and C). This may be extended for as many items as are listed.

[0204] Also, as used herein, the word “signal” refers to, among other things, indicating something to a corresponding decoder. For example, in certain embodiments the encoder signals a particular one of a plurality of parameters for region-based filter parameter selection for de-artifact filtering. In this way, in an embodiment the same parameter is used at both theencoder side and the decoder side. Thus, for example, an encoder can transmit (explicit signaling) a particular parameter to the decoder so that the decoder can use the same particular parameter. Conversely, if the decoder already has the particular parameter as well as others, then signaling can be used without transmitting (implicit signaling) to simply allow the decoder to know and select the particular parameter. By avoiding transmission of any actual functions, a bit savings is realized in various embodiments. It is to be appreciated that signaling can be accomplished in a variety of ways. For example, one or more syntax elements, flags, and so forth are used to signal information to a corresponding decoder in various embodiments. While the preceding relates to the verb form of the word “signal”, the word “signal” can also be used herein as a noun.

[0205] Implementations can produce a variety of signals formatted to carry information that can be, for example, stored or transmitted. The information can include, for example, instructions for performing a method, or data produced by one of the described implementations. For example, a signal can be formatted to carry the bitstream of a described embodiment. Such a signal can be formatted, for example, as an electromagnetic wave (for example, using a radio frequency portion of spectrum) or as a baseband signal. The formatting can include, for example, encoding a data stream and modulating a carrier with the encoded data stream. The information that the signal carries can be, for example, analog or digital information. The signal can be transmitted over a variety of different wired or wireless links, as is known. The signal can be stored on a processor-readable medium.

[0206] We describe a number of embodiments. Features of these embodiments can be provided alone or in any combination, across various claim categories and types. Further, embodiments can include one or more of the following features, devices, or aspects, alone or in any combination, across various claim categories and types:

[0207] A bitstream or signal that includes one or more of the described syntax elements, or variations thereof.

[0208] A bitstream or signal that includes syntax conveying information generated according to any of the embodiments described.

[0209] Creating and / or transmitting and / or receiving and / or decoding a bitstream or signal that includes one or more of the described syntax elements, or variations thereof.

[0210] Creating and / or transmitting and / or receiving and / or decoding according to any of the embodiments described.

[0211] A method, process, apparatus, medium storing instructions, medium storing data, or signal according to any of the embodiments described.

[0212] Note that various hardware elements of one or more of the described embodiments may be referred to as “modules” that carry out (i.e., perform, execute, and the like) various functions that are described herein in connection with the respective modules. As used herein, a module includes hardware (e.g., one or more processors, one or more microprocessors, one or more microcontrollers, one or more microchips, one or more application-specific integrated circuits (ASICs), one or more field programmable gate arrays (FPGAs), one or more memory devices) deemed suitable for a given implementation. Each described module may also include instructions executable for carrying out the one or more functions described as being carried out by the respective module, and it is noted that those instructions could take the form of or include hardware (i.e., hardwired) instructions, firmware instructions, software instructions, and / or the like, and may be stored in any suitable non-transitory computer- readable medium or media, such as commonly referred to as RAM, ROM, etc.

[0213] Although features and elements are described above in particular combinations, each feature or element can be used alone or in any combination with the other features and elements. In addition, the methods described herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer-readable storage media include, but are not limited to, a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks, and digital versatile disks (DVDs). A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, UE, terminal, base station, RNC, or any host computer.

Claims

CLAIMS1. An encoding method comprising: encoding a first parameter set of a volumetric video bitstream, including: performing a first iteration through one or more indices associated with respective atlases; and for each index in the first iteration, encoding an associated atlas identifier of the respective atlas; and encoding a second parameter set for one or more sub-bitstreams of the volumetric video bitstream including: performing a second iteration through the one or more indices; for each index in the second iteration, determining the associated alas identifier and encoding a plurality of parameters for the atlas identified by the associated atlas identifier.

2. An encoding apparatus comprising one or more processors configured to perform at least: encoding a first parameter set of a volumetric video bitstream, including: performing a first iteration through one or more indices associated with respective atlases; and for each index in the first iteration, encoding an associated atlas identifier of the respective atlas; and encoding a second parameter set for one or more sub-bitstreams of the volumetric video bitstream including: performing a second iteration through the one or more indices; for each index in the second iteration, determining the associated alas identifier and encoding a plurality of parameters for the atlas identified by the associated atlas identifier.

3. The method of claim 1 or the apparatus of claim 2, further comprising encoding in the first parameter set a parameter indicating a number of atlases in the volumetric video bitstream,wherein a number of iterations performed in the first and the second iterations is determined by the indicated number.

4. The method of claim 1 , or claim 3 as it depends from claim 1 , or the apparatus of claim 2, or claim 3 as it depends from claim 2, wherein the first parameter set is a V3C parameter set.

5. The method of claim 1 , or claims 3-4 as they depend from claim 1 , or the apparatus of claim 2, or claims 3-4 as they depend from claim 2, wherein the second parameter set is a video parameter set, VPS, extension for video-based dynamic mesh coding, VDMC.

6. The method of claim 1 , or claims 3-4 as they depend from claim 1 , or the apparatus of claim 2, or claims 3-4 as they depend from claim 2, wherein the plurality of parameters include a codec identifier of the respective atlas.

7. The method of claim 1 , or claims 3-4 as they depend from claim 1 , or the apparatus of claim 2, or claims 3-4 as they depend from claim 2, wherein the plurality of parameters include a frame width and a frame height of the respective atlas.

8. A decoding method comprising: decoding a first parameter set of a volumetric video bitstream, including: performing a first iteration through one or more indices associated with respective atlases; and for each index in the first iteration, decoding an associated atlas identifier of the respective atlas; and decoding a second parameter set for one or more sub-bitstreams of the volumetric video bitstream including: performing a second iteration through the one or more indices; and for each index in the second iteration, determining the associated alas identifier and decoding a plurality of parameters for the atlas identified by the associated atlas identifier.

9. A decoding apparatus comprising one or more processors configured to perform: decoding a first parameter set of a volumetric video bitstream, including: performing a first iteration through one or more indices associated with respective atlases; and for each index in the first iteration, decoding an associated atlas identifier of the respective atlas; and decoding a second parameter set for one or more sub-bitstreams of the volumetric video bitstream including: performing a second iteration through the one or more indices; and for each index in the second iteration, determining the associated alas identifier and decoding a plurality of parameters for the atlas identified by the associated atlas identifier.

10. The method of claim 8 or the apparatus of claim 9, further comprising decoding from the first parameter set a parameter indicating a number of atlases in the volumetric video bitstream, wherein a number of iterations performed in the first and the second iterations is determined by the indicated number.11 . The method of claim 8, or claim 10 as it depends from claim 8, or the apparatus of claim 9, or claim 10 as it depends from claim 9, wherein the first parameter set is a V3C parameter set.

12. The method of claim 8, or claims 10-11 as they depend from claim 8, or the apparatus of claim 9, or claims 10-11 as they depend from claim 9, wherein the second parameter set is a video parameter set, VPS, extension for video-based dynamic mesh coding, VDMC.

13. The method of claim 8, or claims 10-12 as they depend from claim 8, or the apparatus of claim 9, or claims 10-12 as they depend from claim 9, wherein the plurality of parameters include a codec identifier of the respective atlas.

14. The method of claim 8, or claims 10-13 as they depend from claim 8, or the apparatus of claim 9, or claims 10-13 as they depend from claim 9, wherein the plurality of parameters include a bit depth of the respective atlas.

15. The method of claim 8, or claims 10-14 as they depend from claim 8, or the apparatus of claim 9, or claims 10-14 as they depend from claim 9, wherein the plurality of parameters include a frame width and a frame height of the respective atlas.

Images