Adaptive Quantization for Instance-Based Mesh Coding

Abstract

1. A method and apparatus, comprising: computer code configured to: cause one or more processors to obtain an input mesh including volumetric data for at least one three-dimensional (3D) visual content; derive a plurality of submeshes of the input mesh from frames of the volumetric data; set a bit depth for a first submesh and a second submesh from the submeshes, the first bit depth being different from the second bit depth; quantize the first submesh and the second submesh based on the first bit depth and the second bit depth, respectively; and signal a result of quantizing the first submesh and the second submesh.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 359,749, filed July 8, 2022, and U.S. Patent Application No. 18 / 312,675, filed May 5, 2023, the disclosures of which are incorporated by reference in their entireties herein.

[0002] This disclosure is directed to a set of advanced video coding techniques, including both lossless and lossy mesh coding techniques based on mesh instances and bit depth. [Background technology]

[0003] Advances in 3D capture, modeling, and rendering are facilitating the ubiquitous presence of 3D content across several platforms and devices. Today, it is possible to film a baby's first steps on one continent while the baby's grandparents on another continent can view (and possibly interact with) that child and enjoy a fully immersive experience with that child. Yet, to achieve such realism, models are becoming ever more sophisticated, and significant amounts of data are linked to the creation and consumption of these models.

[0004] VMesh is an ongoing MPEG standard for compressing static and dynamic meshes. VMesh separates an input mesh into a simplified base mesh and a residual mesh. The base mesh can be encoded at high quality, while the remaining mesh can be encoded using subdivision surface fitting and displacement encoding to exploit local properties.

[0005] However, complex meshes often contain information about multiple instances to associate and link texture maps. This information is available at the time of encoding. On the other hand, meshes can also be segmented into several parts based on their characteristics. For example, there are more polygons in the face region of a human mesh.

[0006] Therefore, a constant quantization step size applied to all instances, objects, parts in a mesh leads to large quantization errors, mesh regions may not be equally important, the number of faces may vary significantly in different parts of the mesh, the base mesh may be simpler than the original mesh and displacements may therefore require less bit depth precision, etc. Therefore, for any of these reasons, a technical solution to such problems that arise in video coding technology is desired. Summary of the Invention [Means for solving the problem]

[0007] Methods and apparatuses are included that include a memory configured to store computer program code and one or more processors configured to access the computer program code and act as instructed by the computer program code. The computer program is configured to cause the processor to execute: an acquisition code configured to cause the at least one processor to acquire volumetric data of at least one three-dimensional (3D) visual content; a derivation code configured to cause the at least one processor to derive a plurality of sub-meshes from a frame of the volumetric data, each of the sub-meshes including a respective one of the instances of the object, and at least two of the sub-meshes overlap each other in the frame; a setting code configured to cause the at least one processor to set a first bit depth to a first sub-mesh of the at least two of the sub-meshes and a second bit depth to a second sub-mesh of the at least two of the sub-meshes, the first bit depth being different from the second bit depth; a quantization code configured to cause the at least one processor to quantize at least two of the sub-meshes based on each of the first bit depth and the second bit depth; and a signaling code configured to cause the at least one processor to signal a result of quantizing the at least two of the sub-meshes.

[0008] According to various embodiments, the volumetric data includes at least two of the sub-meshes that overlap each other and are surrounded by bounding boxes, and deriving the plurality of sub-meshes includes surrounding each of the instances of the object with a respective second bounding box, and in either the first bit depth or the second bit depth, a quantization step size of any of the at least two of the sub-meshes is smaller than a quantization step size of at least two of the sub-meshes that overlap each other and are surrounded by bounding boxes.

[0009] According to various embodiments, setting the first bit depth is based on determining a first areal density of a first submesh of the at least two of the submeshes, and setting the second bit depth is based on determining a second areal density of a second submesh of the at least two of the submeshes.

[0010] According to various embodiments, quantizing at least two of the submeshes includes applying a first level of quantization to a first submesh of the at least two of the submeshes based on a first bit depth, and applying a second level of quantization to a second submesh of the at least two of the submeshes based on a second bit depth, the first level being set to be lower than the second level based on determining that the first bit depth indicates that the first submesh of the at least two of the submeshes has one of the areal densities greater than is indicated by the second bit depth set for the second submesh of the at least two submeshes.

[0011] According to various embodiments, a first of the at least two submeshes is surrounded by a first of the second bounding boxes and a second of the at least two submeshes is surrounded by a second of the second bounding boxes, and determining the first and second areal densities includes comparing a number of faces of the first of the at least two submeshes and the second of the at least two submeshes to a volume of the first of the second bounding boxes and the second of the second bounding boxes, respectively.

[0012] According to various embodiments, signaling the result of quantizing at least two of the sub-meshes includes signaling that each of the at least two of the sub-meshes share the same bounding box offset.

[0013] According to various embodiments, signaling the results of quantizing at least two of the sub-meshes includes signaling a total number of instances of the object in the frame.

[0014] According to various embodiments, signaling the results of quantizing at least two of the submeshes includes signaling a difference between the quantization applied to at least two of the submeshes and sorting the differences compared to other quantizations applied to other submeshes of the frame.

[0015] According to various embodiments, the first bit depth is applied to at least one other submesh of the other submeshes, and signaling the result of quantizing the at least two of the submeshes includes grouping the first submesh of the at least two of the submeshes with the at least one other submesh of the other submeshes based on determining that the first bit depth is applied to both the first submesh of the at least two of the submeshes and the at least one other submesh of the other submeshes.

[0016] According to various embodiments, setting the first bit depth and the second bit depth includes deriving a mean squared error for each of the at least two sub-meshes at each of the first bit depth and the second bit depth. Further features, nature and various advantages of the disclosed subject matter will become more apparent from the following detailed description and the accompanying drawings. [Brief description of the drawings]

[0017] [Figure 1]FIG. 2 is a schematic diagram according to an embodiment. [Diagram 2] FIG. 2 is a simplified block diagram according to an embodiment. [Diagram 3] 1 is a schematic diagram according to an embodiment. [Figure 4] 1 is a schematic diagram according to an embodiment. [Diagram 5] 1 is a schematic diagram according to an embodiment. [Figure 6] 1 is a schematic diagram according to an embodiment. [Figure 7] 1 is a schematic diagram according to an embodiment. [Figure 8] 1 is a schematic diagram according to an embodiment. [Figure 9] 1 is a schematic diagram according to an embodiment. [Figure 10] 1 is a schematic diagram according to an embodiment. [Figure 11] 1 is a schematic diagram according to an embodiment. [Figure 12] 1 is a schematic diagram according to an embodiment. [Figure 13] FIG. 2 is a simplified flow diagram according to an embodiment. [Figure 14] FIG. 2 is a simplified flow diagram according to an embodiment. [Figure 15] FIG. 2 is a simplified flow diagram according to an embodiment. [Figure 16] 1 is a schematic diagram according to an embodiment. [Figure 17] 1 is a schematic diagram according to an embodiment. [Figure 18] 1 is a schematic diagram according to an embodiment. [Figure 19] 1 is a schematic diagram according to an embodiment. [Figure 20] FIG. 2 is a simplified flow diagram according to an embodiment. [Figure 21] 1 is a schematic diagram according to an embodiment. [Figure 22] FIG. 2 is a simplified flow diagram according to an embodiment. [Figure 23] 1 is a schematic diagram according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The proposed features discussed below may be used separately or combined in any order. Furthermore, the embodiments may be implemented by processing circuitry (e.g., one or more processors or one or more integrated circuits). In one example, the one or more processors execute a program stored on a non-transitory computer-readable medium.

[0019] 1 illustrates a simplified block diagram of a communication system 100 according to one embodiment of the present disclosure. The communication system 100 may include at least two terminals 102, 103 interconnected via a network 105. In the case of unidirectional transmission of data, a first terminal 103 may code video data at a local location for transmission to the other terminal 102 via the network 105. The second terminal 102 may receive the coded video data of the other terminal from the network 105, decode the coded data, and display the recovered video data. Unidirectional data transmission may be common in media serving applications, etc.

[0020] 1 illustrates a second pair of terminals 101, 104 provided to support bidirectional transmission of coded video, such as may occur during a video conference. For bidirectional transmission of data, each terminal 101, 104 may code video data captured at a local location for transmission to the other terminal over network 105. Each terminal 101, 104 may also receive coded video data transmitted by the other terminal, decode the coded data, and display the recovered video data on a local display device.

[0021] In FIG. 1, the terminals 101, 102, 103, 104 may be illustrated as a server, a personal computer, and a smartphone, although the principles of the present disclosure are not so limited. The embodiments of the present disclosure also apply to laptop computers, tablet computers, media players, and / or dedicated video conferencing equipment. The network 105 represents any number of networks that convey coded video data between the terminals 101, 102, 103, 104, including, for example, wired and / or wireless communication networks. The communication network 105 may exchange data in circuit-switched and / or packet-switched channels. Representative networks include telecommunications networks, local area networks, wide area networks, and / or the Internet. For purposes of this discussion, the architecture and topology of the network 105 may not be important to the operation of the present disclosure unless described below in this specification.

[0022] 2 illustrates the arrangement of a video encoder and a video decoder in a streaming environment as one example of an application of the disclosed subject matter. The disclosed subject matter may be equally applicable to other video-enabled applications including, for example, video conferencing, digital television, storage of compressed video on digital media including CDs, DVDs, memory sticks, and the like.

[0023] The streaming system may include a capture subsystem 203, which may include a video source 201, such as a digital camera, that creates an uncompressed video sample stream 213. The sample stream 213 may be highlighted as a high data volume when compared to an encoded video bitstream and may be processed by an encoder 202 coupled to the video source 201, which may be a camera as described above. The encoder 202 may include hardware, software, or a combination thereof to enable or implement aspects of the disclosed subject matter, as described in more detail below. The encoded video bitstream 204 may be highlighted as a lower data volume when compared to the sample stream and may be stored on a streaming server 205 for future use. One or more streaming clients 212, 207 may access the streaming server 205 to retrieve copies 208, 206 of the encoded video bitstream 204. The client 212 may include a video decoder 211 that decodes a copy 208 of an input encoded video bitstream and creates an output video sample stream 210 that can be rendered on a display 209 or other rendering device (not shown). In some streaming systems, the video bitstreams 204, 206, 208 may be encoded according to a particular video coding / compression standard. Examples of these standards are mentioned above and further described herein.

[0024] FIG. 3 may be a functional block diagram of a video decoder 300 according to one embodiment of the present invention.

[0025] The receiver 302 may receive one or more codec video sequences to be decoded by the decoder 300, in the same or other embodiments, one coded video sequence at a time, with the decoding of each coded video sequence being independent of the other coded video sequences. The coded video sequences may be received from a channel 301, which may be a hardware / software link to a storage device that stores the encoded video data. The receiver 302 may receive the encoded video data together with other data, e.g., coded audio data and / or auxiliary data streams, that may be forwarded to a respective usage entity (not shown). The receiver 302 may separate the coded video sequence from the other data. To combat network jitter, a buffer memory 303 may be coupled between the receiver 302 and the entropy decoder / parser 304 (hereinafter, "parser"). If the receiver 302 is receiving data from a storage / forwarding device with sufficient bandwidth and controllability, or from an isosynchronous network, the buffer 303 may not be needed or may be small. For use over a best effort packet network such as the Internet, buffer 303 may be required and may be relatively large, and may advantageously be of adaptive size.

[0026] The video decoder 300 may include a parser 304 for reconstructing symbols 313 from the entropy coded video sequence. The categories of symbols include information used to manage the operation of the decoder 300 and information for controlling a rendering device, such as a display 312, which is potentially not an integral part of the decoder but may be coupled to the decoder. The control information for the rendering device(s) may be in the form of a Supplementary Enhancement Information (SEI message) or a Video Usability Information (VUI) parameter set fragment (not shown). The parser 304 may parse / entropy decode the received coded video sequence. The coding of the coded video sequence may be in accordance with a video coding technique or standard and may follow principles well known to those skilled in the art, including variable length coding, Huffman coding, arithmetic coding with or without context sensitivity, etc. The parser 304 may extract from the coded video sequence a set of subgroup parameters for at least one of the subgroups of pixels in the video decoder based on at least one parameter corresponding to the group. Subgroups may include Groups of Pictures (GOPs), pictures, tiles, slices, macroblocks, coding units (CUs), blocks, transform units (TUs), prediction units (PUs), etc. The entropy decoder / parser may also extract information such as transform coefficients, quantization parameter values, motion vectors, etc. from the coded video sequence.

[0027] The parser 304 may perform an entropy decoding / parsing operation on the video sequence received from the buffer 303 to produce symbols 313. The parser 304 may receive the encoded data and selectively decode particular symbols 313. Additionally, the parser 304 may determine whether a particular symbol 313 should be provided to the motion compensated prediction unit 306, the scaler / inverse transform unit 305, the intra prediction unit 307, or the loop filter 311.

[0028] The reconstruction of symbols 313 may involve several different units, depending on the type of coded video picture or portion thereof (inter-picture and intra-picture, inter-block and intra-block, etc.), as well as other factors. Which units are involved and how can be controlled by subgroup control information parsed from the coded video sequence by parser 304. The flow of such subgroup control information between parser 304 and the following units is not shown for clarity.

[0029] Besides the functional blocks already mentioned, the decoder 300 can be conceptually subdivided into several functional units as described below. In a practical implementation operating under commercial constraints, many of these units will interact closely with each other and may be at least partially integrated with each other. However, for the purposes of describing the disclosed subject matter, the following conceptual subdivision into functional units is adequate:

[0030] The first unit is a scalar / inverse transform unit 305. The scalar / inverse transform unit 305 receives quantized transform coefficients and control information from the parser 304 as symbol(s) 313, including the transform to use, block size, quantization coefficients, quantization scaling matrix, etc. The scalar / inverse transform unit 305 may output a block containing sample values ​​that may be input to an aggregator 310.

[0031] In some cases, the output samples of the scalar / inverse transform unit 305 may also relate to intra-coded blocks, i.e. blocks that do not use prediction information from a previously reconstructed picture, but can use prediction information from a previously reconstructed part of the current picture. Such prediction information may be provided by the intra-picture prediction unit 307. In some cases, the intra-picture prediction unit 307 generates a block of the same size and shape as the block being reconstructed using surrounding already reconstructed information fetched from the current (partially reconstructed) picture 309. The aggregator 310 adds, possibly on a sample-by-sample basis, the prediction information generated by the intra-prediction unit 307 to the output sample information provided by the scalar / inverse transform unit 305.

[0032] In other cases, the output samples of the scalar / inverse transform unit 305 may relate to an inter-coded, potentially motion-compensated block. In such cases, the motion compensated prediction unit 306 may access the reference picture memory 308 to fetch samples used for prediction. After motion compensating the fetched samples according to the symbols 313 relating to the block, these samples may be added to the output of the scalar / inverse transform unit by the aggregator 310 to generate output sample information (in this case referred to as residual samples or residual signals). The addresses in the reference picture memory format from which the motion compensation unit fetches the prediction samples may be controlled by the motion vector and made available to the motion compensation unit in the form of symbols 313, which may have, for example, X, Y, and reference picture components. Motion compensation may also include interpolation of sample values ​​fetched from the reference picture memory when a sub-sample accurate motion vector is in use, motion vector prediction mechanisms, etc.

[0033] The output samples of the aggregator 310 may be subjected to various loop filtering techniques in a loop filter unit 311. The video compression techniques may include in-loop filter techniques controlled by parameters contained in the coded video bitstream and made available to the loop filter unit 311 as symbols 313 from the parser 304, but may also be responsive to meta-information obtained during decoding of a previous part (in decoding order) of the coded picture or coded video sequence, or may be responsive to previously reconstructed, loop filtered sample values.

[0034] The output of the loop filter unit 311 may be a sample stream that can be output to the rendering device 312 and also stored in the reference picture memory 557 for use in future inter-picture prediction.

[0035] Once a particular coded picture is fully reconstructed, it can be used as a reference picture for future prediction. Once a coded picture is fully reconstructed and the coded picture is identified as a reference picture (e.g., by parser 304), the current reference picture 309 can become part of reference picture buffer 308, and a new current picture memory can be reallocated before beginning reconstruction of a subsequent coded picture.

[0036] The video decoder 300 may perform decoding operations according to a given video compression technique documented in a standard such as ITU-T Rec. H.265. The coded video sequence may conform to the syntax specified by the video compression technique or standard used in the sense of adhering to the syntax of the video compression technique or standard as specified in the video compression technique document or standard, specifically in a profile document therein. It may also be necessary for compliance that the complexity of the coded video sequence be within a range defined by the level of the video compression technique or standard. In some cases, the level limits a maximum picture size, a maximum frame rate, a maximum reconstruction sample rate (e.g., measured in megasamples per second), a maximum reference picture size, etc. The limits set by the level may be further constrained in some cases by a Hypothetical Reference Decoder (HRD) specification and metadata for HRD buffer management signaled in the coded video sequence.

[0037] In one embodiment, the receiver 302 may receive additional (redundant) data along with the encoded video. The additional data may be included as part of the coded video sequence(s). The additional data may be used by the video decoder 300 to properly decode the data and / or to more accurately reconstruct the original video data. The additional data may be in the form of, for example, a temporal layer, a spatial layer, or a signal-to-noise ratio (SNR) enhancement layer, redundant slices, redundant pictures, forward error correction codes, etc.

[0038] FIG. 4 may be a functional block diagram of a video encoder 400 according to one embodiment of the present disclosure.

[0039] The encoder 400 may receive video samples from a video source 401 (not part of the encoder), which may capture the video image(s) to be coded by the encoder 400 .

[0040] The video source 401 may provide a source video sequence to be coded by the encoder (303) in the form of a digital video sample stream that may be of any suitable bit depth (e.g., 8-bit, 10-bit, 12-bit, ...), any color space (e.g., BT.601 Y CrCB, RGB, ...) and suitable sampling structure (e.g., Y CrCb 4:2:0, Y CrCb 4:4:4). In a media serving system, the video source 401 may be a storage device that stores previously prepared video. In a video conferencing system, the video source 401 may be a camera that captures local image information as a video sequence. The video data may be provided as multiple individual pictures that convey motion when viewed in sequence. The pictures themselves may be organized as a spatial array of pixels, each of which may contain one or more samples depending on the sampling structure, color space, etc. in use. Those skilled in the art can easily understand the relationship between pixels and samples. The following description focuses on samples.

[0041] According to an embodiment, the encoder 400 may code and compress pictures of a source video sequence into a coded video sequence 410 in real time or under any other time constraint required by the application. Imposing an appropriate coding rate is one function of the controller 402. The controller controls and is operatively coupled to other functional units as described below. Coupling is not shown for clarity. Parameters set by the controller may include rate control related parameters (picture skip, quantizer, lambda value for rate distortion optimization techniques, ...), picture size, Groups of Pictures (GOP) layout, maximum motion vector search range, etc. Other functions of the controller 402 may be relevant to optimizing the video encoder 400 for a particular system design, and thus may be readily identified by one skilled in the art.

[0042] Some video encoders operate in what those skilled in the art will easily recognize as a "coding loop". As an oversimplified explanation, the coding loop can consist of an encoding part of the encoder 400 (hereafter "source coder"), responsible for creating symbols based on the input picture to be coded and the reference picture(s), and a (local) decoder 406 built into the encoder 400, which reconstructs the symbols to create sample data that the (remote) decoder would also create (since any compression between the symbols and the coded video bitstream is lossless in the video compression techniques considered in the disclosed subject matter). The reconstructed sample stream is input to a reference picture memory 405. The decoding of the symbol stream leads to bit-exact results independent of the location of the decoder (local or remote), so the contents of the reference picture buffer are also bit-exact between the local and remote encoders. In other words, the predictive part of the encoder "sees" exactly the same sample values ​​as the decoder would "see" when using prediction during decoding as reference picture samples. This basic principle of reference picture synchrony (and the resulting drift when synchrony cannot be maintained, eg, due to channel errors) is well known to those skilled in the art.

[0043] The operation of the "local" decoder 406 may be the same as that of the "remote" decoder 300, which has already been described in detail above in relation to Figure 3. However, with brief reference also to Figure 4, because symbols are available and the encoding / decoding of symbols into a coded video sequence by the entropy coder 408 and the parser 304 may be lossless, the entropy decoding portion of the decoder 300, including the channel 301, the receiver 302, the buffer 303, and the parser 304, may not be fully implemented in the local decoder 406.

[0044] At this point, it can be said that any decoder technology, other than parsing / entropy decoding, present in the decoder must necessarily also be present in the corresponding encoder in substantially the same functional form. The description of the encoder technology can be omitted, since it is the inverse of the decoder technology, which has been described generically. Only in certain areas is a more detailed description necessary, which is provided below.

[0045] As part of its operation, the source coder 403 may perform motion-compensated predictive coding, which predictively codes an input frame with reference to one or more previously coded frames from the video sequence designated as “reference frames.” In this manner, the coding engine 407 codes differences between pixel blocks of the input frame and pixel blocks of the reference frame(s) that may be selected as the predictive reference(s) to the input frame.

[0046] The local video decoder 406 may decode the coded video data of the frames, which may be designated as reference frames, based on the symbols created by the source coder 403. The operation of the coding engine 407 may advantageously be a lossy process. If the coded video data may be decoded in a video decoder (not shown in FIG. 4), the reconstructed video sequence may be a copy of the source video sequence, usually with some errors. The local video decoder 406 may reproduce the decoding process that may be performed by the video decoder on the reference frames, and store the reconstructed reference frames in a reference picture memory 405, which may be, for example, a cache. In this way, the encoder 400 may locally store copies of the reconstructed reference frames that have a common content as the reconstructed reference frames to be obtained by the far-end video decoder (without transmission errors).

[0047] The predictor 404 may perform a predictive search for the coding engine 407. That is, for a new frame to be coded, the predictor 404 may search the reference picture memory 405 for sample data (as candidate reference pixel blocks) or specific metadata such as reference picture motion vectors, block shapes, etc., that may serve as suitable predictive references for the new picture. The predictor 404 may operate on sample blocks by pixel blocks to find suitable predictive references. In some cases, as determined by the search results obtained by the predictor 404, the input picture may have predictive references drawn from multiple reference pictures stored in the reference picture memory 405.

[0048] The controller 402 may manage the coding operations of a source coder 403, which may be, for example, a video coder, including, for example, setting parameters and subgroup parameters used to encode the video data.

[0049] The output of all the aforementioned functional units may be subjected to entropy coding in an entropy coder 408. The entropy coder converts the symbols produced by the various functional units into a coded video sequence by losslessly compressing the symbols according to techniques known to those skilled in the art, such as, for example, Huffman coding, variable length coding, arithmetic coding, etc.

[0050] The transmitter 409 may buffer the coded video sequence(s) created by the entropy coder 408 in preparation for transmission over a communication channel 411, which may be a hardware / software link to a storage device that will store the encoded video data. The transmitter 409 may merge the coded video data from the source coder 403 with other data to be transmitted, such as coded audio data and / or ancillary data streams (source not shown).

[0051] The controller 402 may manage the operation of the encoder 400. During coding, the controller 402 may assign a particular coded picture type to each coded picture, which may affect the coding technique that may be applied to the respective picture. For example, pictures may often be assigned as one of the following frame types:

[0052] An intra picture (I-picture) may be a picture that can be coded and decoded without using any other frame in a sequence as a source of prediction. Some video codecs allow various types of intra pictures, including, for example, independent decoder refresh pictures. Those skilled in the art are aware of these variations of I-pictures and their respective uses and characteristics.

[0053] A predictive picture (P picture) may be a picture that can be coded and decoded using intra- or inter-prediction, which uses at most one motion vector and reference index to predict sample values ​​for each block.

[0054] Bidirectionally predicted pictures (B-pictures) may be coded and decoded using intra- or inter-prediction that uses up to two motion vectors and reference indices to predict the sample values ​​of each block. Similarly, multi-predicted pictures may use more than two reference pictures and associated metadata for the reconstruction of a single block.

[0055] A source picture may generally be spatially subdivided into multiple sample blocks (e.g., blocks of 4x4, 8x8, 4x8, or 16x16 samples each) and coded block by block. A block may be predictively coded with reference to other (already coded) blocks as determined by the coding assignment applied to the block's respective picture. For example, a block of an I picture may be non-predictively coded or predictively coded with reference to already coded blocks of the same picture (spatial or intra prediction). A pixel block of a P picture may be non-predictively coded via spatial prediction or via temporal prediction with reference to one previously coded reference picture. A pixel block of a B picture may be non-predictively coded via spatial prediction or via temporal prediction with reference to one or two previously coded reference pictures.

[0056] Encoder 400 may be, for example, a video coder and may perform coding operations according to a given video coding technique or standard, such as ITU-T Rec. H.265. In its operation, encoder 400 may perform various compression operations, including predictive coding operations that exploit temporal and spatial redundancy in an input video sequence. Thus, the coded video data may conform to a syntax specified by the video coding technique or standard being used.

[0057] In one embodiment, the transmitter 409 may transmit additional data along with the encoded video. The source coder 403 may include such data as part of the coded video sequence. The additional data may include temporal / spatial / SNR enhancement layers, other forms of redundant data such as redundant pictures or slices, Supplemental Enhancement Information (SEI) messages, Visual Usability Information (VUI) parameter set fragments, etc.

[0058] FIG. 5 illustrates a simplified block-style workflow diagram 500 of example viewport-dependent processing in Omnidirectional Media Application Format (OMAF) that may enable 360-degree virtual reality (VR360) streaming described in OMAF.

[0059] In acquisition block 1001, video data A is acquired, such as multiple image and audio data of the same time instance, if the image data can represent a scene in VR360. In processing block 1003, image B of the same time instance is acquired. i are processed by one or more of stitching, mapping onto a projected picture for one or more virtual reality (VR) angles or other angles / viewpoints, and packed by region. Additionally, metadata indicating any of such processed and other information may be created to aid in the distribution and rendering processes.

[0060] For data D, in the image encoding block 1005, the projected picture is i In the viewport independent streaming, the video pictures are encoded into a media file and then organized into a media file. In the video encoding block 1004, the video pictures are encoded into a data E, for example, as a single layer bitstream. v and data B is encoded as a Regarding the audio data, the audio data is also encoded in the audio encoding block 1002 as data E a can be encoded into

[0061] Data E a , E v , and E i , the coded bitstream F iand / or the entirety of F may be stored in a (content delivery network (CDN) / cloud) server and typically transmitted in its entirety to the OMAF player 1020 in a distribution block 1007 or otherwise, from the head / eye tracking block 1008, where it may be fully decoded by a decoder such that at least one area of ​​the decoded picture corresponding to the current viewport in terms of various metadata, file playback, and orientation / viewport metadata, such as the angle the user may be looking through the VR imaging device in terms of the viewport specifications of that device, is rendered to the user in a display block 1016. A distinctive feature of VR360 is that only the viewport may be displayed at any particular time, and such a feature may be used to improve the performance of the omnidirectional video system by selective distribution according to the user's viewport (or any other criteria, such as recommended viewport timed metadata). For example, viewport-dependent distribution may be enabled by tile-based video coding according to an exemplary embodiment.

[0062] Similar to the encoding blocks described above, the OMAF player 1020 according to an exemplary embodiment may generate data F′ and / or F′ i and similarly reverse one or more facets of such encoding with respect to file / segment deencapsulation of one or more of the metadata to produce audio data E' in audio decode block 1010. i The video decode block 1013 decodes the video data E' v In the image decoding block 1014, image data E' i and decodes the data A' in VR360 format according to various metadata such as orientation / viewport metadata in a display block 1016. i The speaker / headphone block 1012 outputs the audio data A' s In order to output the data B' in the audio rendering block 1011, aand image rendering of the data D' in audio rendering and image rendering block 1015. It should be understood that various metadata may affect the data decoding and rendering processes depending on various tracks, languages, qualities, views that may be selected by or for a user of the OMAF player 1020, and that the order of processing described herein is presented for an exemplary embodiment and may be performed in other orders according to other exemplary embodiments.

[0063] 6 illustrates a simplified block-style content flow process diagram 600 of (coded) point cloud data with viewpoint- and angle-dependent processing of point cloud data (herein "V-PCC") for 6-DOF media capture / generation / (de)coding / rendering / display. It should be understood that the features described may be used separately or combined in any order, and that elements such as encoding and decoding, among others, illustrated, may be performed by processing circuitry (e.g., one or more processors or one or more integrated circuits), and that the one or more processors may execute a program stored on a non-transitory computer-readable medium according to an exemplary embodiment.

[0064] Diagram 600 illustrates an example embodiment for streaming coded point cloud data with V-PCC.

[0065] In volumetric data acquisition block 1101, a real-world visual scene or a computer-generated visual scene (or a combination thereof) may be captured by a set of camera devices or synthesized by a computer as volumetric data, which may have any format and may be converted to a (quantized) point cloud data format via image processing in conversion to point cloud block 1102. For example, data from the volumetric data may be converted area data-wise into a point of a point cloud by pulling one or more of the values ​​described below from the volumetric data and any associated data into a desired point cloud format according to an exemplary embodiment. According to an exemplary embodiment, the volumetric data may be a 3D dataset of 2D images, such as slices from which 2D projections of the 3D dataset may be projected. According to an example embodiment, a point cloud data format includes a representation of data points in one or more various spaces and may be used to represent volumetric data and may provide improvements with respect to sampling and data compression, such as with respect to temporal redundancy; for example, point cloud data in x, y, z format may represent color values ​​(e.g., RGB, etc.), brightness, intensity, etc. at each of a plurality of points of the cloud data and may also be used in conjunction with progressive decoding, polygon meshing, direct rendering, and octree 3D representation of 2D quadtree data.

[0066] In a projection onto image block 1103, the acquired point cloud data may be projected onto a 2D image and encoded as an image / video picture using video-based point cloud coding (V-PCC). The projected point cloud data may consist of attributes, geometry, occupancy maps, and other metadata used for reconstruction of the point cloud data using, for example, Painter's algorithm, ray casting algorithms, (3D) binary space partitioning algorithms, among others.

[0067] Meanwhile, in the scene generator block 1109, the scene generator may generate some metadata to be used to render and display 6 degrees of freedom (DoF) media, for example according to the director's intent or user's preferences. Such 6DoF media may include 360VR-like 3D viewing of the scene from rotational changes on 3D axes X, Y, Z, in addition to additional dimensions that allow for forward / backward, up / down, and left / right movement within the point cloud coded data or at least with respect to the virtual experience according to it. The scene description metadata defines one or more scenes composed of the coded point cloud data and other media data including VR360, light field, audio, etc., and may be provided to one or more cloud servers and / or file / segment encapsulation / deencapsulation processes as indicated in FIG. 6 and the related description.

[0068] After a video encoding block 1104 and an image encoding block 1105 similar to the video and image encoding described above (it will also be appreciated that audio encoding may also be provided as described above), a file / segment encapsulation block 1106 processes the coded point cloud data so that it is arranged into a media file for file playback or a sequence of default segments and media segments for streaming in a particular media container file format, such as one or more video container formats, and in particular may be used with respect to DASH, described below, such description representing an exemplary embodiment. The file container may also include scene description metadata, such as from a scene generator block 1109, into the file or segment.

[0069] According to an exemplary embodiment, the files are encapsulated according to scene description metadata to each include at least one viewpoint position at one or more times in the 6DoF media and at least one or more angular views at the one or more viewpoint positions, such that such files may be transmitted on demand according to user or creator input. Further, according to an exemplary embodiment, a segment of such a file may include one or more portions of such a file, such as a portion of the 6DoF media indicating a single viewpoint and angle at that viewpoint at one or more times, although these are merely exemplary embodiments and may be modified according to various conditions, such as network, user, creator capabilities and input.

[0070] According to an example embodiment, the point cloud data is divided into multiple 2D / 3D regions, which are coded independently, such as in one or more of the video encoding block 1104 and the image encoding block 1105. Each independently coded partition of the point cloud data may then be encapsulated as a track within a file and / or segment in the file / segment encapsulation block 1106. According to an example embodiment, each point cloud track and / or metadata track may include some useful metadata for viewpoint position / angle dependent processing.

[0071] According to an exemplary embodiment, metadata such as included in a file and / or segment encapsulated with respect to a file / segment encapsulation block useful for viewpoint position / angle dependent processing includes one or more of the following: layout information of 2D / 3D partitions with indexes; (dynamic) mapping information associating 3D volumetric partitions with one or more 2D partitions (e.g. tiles / tile groups / slices / subpictures); 3D position of each 3D partition on the 6DoF coordinate system; a representative viewpoint position / angle list; a selected viewpoint position / angle list corresponding to the 3D volumetric partition; an index of the 2D / 3D partition corresponding to the selected viewpoint position / angle list; information of the quality (rank) of each 2D / 3D partition; and rendering information of each 2D / 3D partition according to, for example, each viewpoint position / angle. Soliciting such metadata when requested, such as by a user of the V-PCC player or as directed by a content creator on behalf of a user of the V-PCC player, may enable more efficient processing with respect to particular portions of the 6DoF media for which such metadata is desired, such that the V-PCC player may deliver a higher quality image of a valued portion of the media than other portions, rather than delivering unused portions of the 6DoF media.

[0072] The file or one or more segments of the file may be delivered from the File / Segment Encapsulation block 1106 using a delivery mechanism (e.g., by Dynamic Adaptive Streaming over HTTP (DASH)) to the V-PCC Player 1125 as well as directly to a cloud server, such as in the Cloud Server block 1107, where the cloud server can extract one or more tracks and / or one or more specific 2D / 3D partitions from the file and merge multiple coded point cloud data into one data.

[0073] If the current viewpoint position and angle(s) are defined on the 6DoF coordinate system at the client system according to data such as position / viewing angle tracking block 1108, the cloud server may extract the appropriate partition(s) from the store file(s) and merge them (if necessary) depending on metadata, for example from a client system having a V-PCC player 1125, and the viewpoint position / angle metadata may be delivered from file / segment encapsulation block 1106 so that the extracted data can be delivered to the client as a file or segment, or may alternatively be processed in other manner in cloud server block 1107 from a file or segment already on the cloud server.

[0074] With regard to such data, in file / segment decapsulation block 1115, a file decapsulator processes the file or received segment, extracts the coded bitstream and parses the metadata, and then in video decode and image decode block, the coded point cloud data is decoded and in point cloud reconstruction block 1112, reconstructed into point cloud data which can be displayed in display block 1114 and / or with regard to scene description data by scene generator block 1109, may be initially configured according to one or more various scene descriptions in scene composition block 1113.

[0075] In view of the above, such an exemplary V-PCC flow represents advantages over the V-PCC standard including one or more of the described partitioning capabilities for multiple 2D / 3D areas, the ability to assemble compressed domains of coded 2D / 3D partitions into a single coherent coded video bitstream, and the bitstream extraction capabilities of the coded 2D / 3D of a coded picture into a coherent coded bitstream, and such V-PCC system support is further improved by the inclusion of a container formation for the VVC bitstream to support a mechanism for housing metadata carrying one or more of the above-mentioned metadata.

[0076] In that regard, according to an exemplary embodiment described further below, the term "mesh" refers to a configuration of one or more polygons that describe the surface of a volumetric object. Each polygon is defined by its vertices in 3D space and information about how the vertices are connected, called connectivity information. Optionally, vertex attributes such as color, normals, etc. may also be associated with the mesh vertices. Attributes may also be associated with the surface of the mesh by utilizing mapping information that parameterizes the mesh with a 2D attribute map. Such mapping may be defined by a set of parametric coordinates, called UV coordinates or texture coordinates, associated with the mesh vertices. The 2D attribute map is used to store high-resolution attribute information such as texture, normals, displacements, etc. Such information may also be used for various purposes, such as texture mapping and shading, according to an exemplary embodiment.

[0077] Nevertheless, dynamic mesh sequences may require a large amount of data since it may consist of a significant amount of information that changes over time. Therefore, efficient compression techniques are needed to store and transmit such content. Mesh compression standards IC, MESHGRID, FAMC were previously developed by MPEG to address dynamic meshes with constant connectivity and time-varying geometry and vertex attributes. However, these standards do not take into account time-varying attribute maps and connectivity information. DCC (Digital Content Creation) tools usually generate such dynamic meshes. Correspondingly, it is difficult for volumetric acquisition techniques to generate constant connectivity dynamic meshes, especially under real-time constraints. This type of content is not supported by existing standards. According to exemplary embodiments herein, aspects of a new mesh compression standard are described for directly processing dynamic meshes with time-varying connectivity information and optionally time-varying attribute maps, which targets lossy and lossless compression for various applications such as real-time communication, storage, free viewpoint video, AR and VR. Features such as random access and scalable / progressive coding will also be considered.

[0078] FIG. 7 represents one dynamic mesh compression example framework 700 for 2D atlas sampling based methods, etc. Each frame of an input mesh 1201 can be pre-processed by a series of operations, e.g., tracking, remeshing, parameterization, voxelization. Note that these operations can be encoder only, meaning that they may not be part of the decoding process, and such a possibility can be signaled in the metadata by a flag, e.g., indicating 0 for encoder only and 1 for others. Then, a mesh with a 2D UV atlas 1202 can be obtained, and each vertex of the mesh has one or more associated UV coordinates on the 2D atlas. The mesh can then be converted into multiple maps, including geometry maps and attribute maps, by sampling on the 2D atlas. These 2D maps can then be coded by video / image codecs, such as HEVC, VVC, AV1, AVS3, etc. At the decoder 1203 side, a mesh can be reconstructed from the decoded 2D maps. Any post-processing and filtering can also be applied to the reconstructed mesh 1204. Note that other metadata may be signaled to the decoder side for the purpose of 3D mesh reconstruction. Note that chart boundary information, including uv and xyz coordinates of the boundary vertices, can be predicted, quantized and entropy coded in the bitstream. The quantization step size can be configured at the encoder side for a tradeoff between quality and bitrate.

[0079] In some implementations, a 3D mesh can be partitioned into several segments (or patches / charts). Each segment consists of a set of connected vertices associated with their geometry, attributes, and connectivity information. As illustrated in the volumetric data example 800 in FIG. 8, the UV parameterization process 1302 of mapping 3D mesh segments onto a 2D chart, such as the 2D UV atlas 1202 block described above, maps one or more mesh segments 1301 onto a 2D chart 1303 in the 2D UV atlas 1304. Each vertex (v n ) will be assigned 2D UV coordinates in the 2D UV atlas. n Note that vertices v1, v2, and v3 form a connected component as their 3D corresponding vertices. The geometry, attributes, and connectivity information of each vertex can be inherited from their 3D counterparts as well. For example, if vertex v4 is connected to vertex v 0、 v 5、 Information about the direct connections to v1, v3 may be indicated, and similar information for each of the other vertices may be supported as well. Furthermore, such a 2D texture mesh, according to an exemplary embodiment, would further indicate information, such as color information, on a patch by patch basis for each triangle, e.g., patches v2, v5, v3.

[0080] For example, see example 900 of FIG. 9, where in addition to the features of example 800 of FIG. 8, a 3D mesh segment 1301 can also be mapped to multiple separate 2D charts 1401, 1402. In this case, a vertex in 3D can also correspond to multiple vertices in the 2D UV atlas. As shown in FIG. 9, the same 3D mesh segment is mapped to multiple 2D charts in the 2D UV atlas, instead of a single chart as in FIG. 8. For example, 3D vertices v1, v4 have two 2D correspondences v1, v4, respectively. 1’ and v4, v 4’Thus, a typical 2D UV atlas of a 3D mesh may consist of multiple charts as shown in Figure 14, where each chart may contain multiple vertices (usually three or more) associated with their 3D geometry, attributes, and connectivity information.

[0081] FIG. 10 shows an example 1000 illustrating the derived triangulation in a chart with boundary vertices B0, B1, B2, B3, B4, B5, B6, B7. When such information is presented, any triangulation method can be applied to create connectivity between vertices (including boundary vertices and sampled vertices). For example, for each vertex, find the two closest vertices. Or, for every vertex, generate triangles successively until a minimum number of triangles is achieved after a set number of attempts. As shown in the example 1000, there are repeating triangles of various regular shapes and triangles of various irregular shapes, which are generally closest to the boundary vertices and have their own unique dimensions that may or may not be shared with any other triangles. The connectivity information can also be reconstructed by explicit signaling. If the polygon cannot be restored by implicit rules, the encoder can signal the connectivity information in the bitstream according to an exemplary embodiment.

[0082] Turning to the patches discussed above, the example 1000 may represent one such patch, such as the patch formed from vertices v3, v2, and v5 shown in either FIG. 14 or FIG.

[0083] Boundary vertices B0, B1, B2, B3, B4, B5, B6, B7 are defined in 2D UV space. As shown in Figure 15, a filled vertex is a boundary vertex because it is on the boundary edge of a connected component (patch / chart). A boundary edge can be determined by checking if the edge appears in only one triangle. The following information of a boundary vertex is important and needs to be signaled in the bitstream according to an exemplary embodiment: Geometry information, e.g., 3D XYZ coordinates even if currently in 2D UV parameter format, and 2D UV coordinates.

[0084] For the case where a bounding vertex in 3D corresponds to multiple vertices in the 2D UV atlas, the mapping from 3D XUZ to 2D UV can be one-to-many, as shown in Figure 9. Therefore, a UV to XYZ (or called UV2XYZ) index can be signaled to indicate the mapping function. UV2XYZ can be a 1D array of indexes that maps each 2D UV vertex to a 3D XYZ vertex.

[0085] According to an example embodiment, to efficiently represent a mesh signal, a subset of mesh vertices may be first coded along with connectivity information between them. In the original mesh, connections between these vertices may not exist because the vertices are subsampled from the original mesh. There are various ways to signal connectivity information between vertices, and therefore such a subset is referred to as a base mesh or base vertices.

[0086] However, other vertices can be predicted by applying interpolation between two or more already decoded mesh vertices. A predictor vertex has its geometric position along the edges of two connected existing vertices, so the geometric information of the predictor can be calculated based on the decoded vertices in the neighborhood. In some cases, a displacement vector or a prediction error from the vertex to be coded to the vertex predictor should be further coded. See, for example, example 1100 of FIG. 11, where an example of such edge-based vertex prediction is shown, more specifically, an example of vertex geometry prediction using extrapolation by extending a triangle into a parallelogram as shown on the left, and intra-prediction by interpolation by a weighted average of two existing vertices as shown on the right. After decoding the base vertices (i.e., solid triangles 1801 on the left of FIG. 11), the interpolation between these base vertices can be performed along the connecting edges. For example, the midpoints of each edge can be generated as predictors. The geometric position of these interpolated points is therefore the (weighted) average of the two nearby decoded vertices (dashed points 1802 on the left of FIG. 11). Having more than one midpoint between two already decoded vertices can also be done in a similar way. Thus, the actual vertices to be coded can be reconstructed by adding the displacement vector to the predictor (Fig. 7 center). After decoding these additional vertices, the connections between the newly decoded vertices and the existing base vertices are still maintained. In addition, further connections between the newly decoded vertices can be established. Along with the base vertices, more midpoint vertex predictors can be generated along new edges (Fig. 7 right) by connecting these newly decoded vertices 1803 and the base vertex to each other. Thus, there are more actual vertices to be decoded with associated displacement vectors.

[0087] According to an example embodiment, mesh vertices of mesh frame 1902 can also be predicted from the decoded vertices of the previously coded mesh frame 1901. This prediction mechanism is called inter prediction. An example of mesh geometry inter prediction is shown in example 1200 of FIG. 12 showing vertex geometry prediction using inter prediction (vertices of the previous mesh frame become predictors of vertices of the current frame). In some cases, a displacement vector or a prediction error from the vertex to be coded to the vertex predictor should also be coded.

[0088] According to an exemplary embodiment, several methods are implemented for dynamic mesh compression, which are part of the edge-based vertex prediction framework described above, where a base mesh is first coded and then more additional vertices are predicted based on connectivity information from the edges of the base mesh. It should be noted that the methods can be applied individually or in any form of combination.

[0089] Consider, for example, vertex grouping for the example flowchart 1300 of prediction modes in FIG. 13. In S201, vertices in a mesh may be obtained and in S202, they may be divided into different groups for prediction purposes, see, for example, FIG. 10. In one example, the division is done using patch / chart partitioning in S204 as previously discussed. In another example, the division is done under each patch / chart S205. The decision S203 to proceed to S204 or S205 may be signaled by a flag or the like. For S205, some vertices of the same patch / chart form a prediction group and share the same prediction mode, while some other vertices of the same patch / chart may use other prediction modes. Such grouping in S206 may be assigned at different levels by determining the number of respective vertices involved per group. For example, every 64, 32, or 16 vertices by scan order in a patch / chart may be assigned the same prediction mode according to an example embodiment, and other vertices may be assigned differently. For each group, the prediction mode can be an intra prediction mode or an inter prediction mode, which can be signaled or assigned. According to the example flowchart 1300, if a mesh frame or mesh slice is determined to be an intra type, such as by checking whether a flag of the mesh frame or mesh slice indicates an intra type in S207, all vertex groups in the mesh frame or mesh slice shall use an intra prediction mode; otherwise, in S208, either an intra prediction mode or an inter prediction mode may be selected for each group for all vertices therein.

[0090] Furthermore, for a group of mesh vertices using intra prediction mode, the vertices can only be predicted by using previously coded vertices in the same subpartition of the current mesh. The subpartition may sometimes be the current mesh itself according to an exemplary embodiment, and for a group of mesh vertices using inter prediction mode, the vertices can only be predicted by using previously coded vertices from other mesh frames according to an exemplary embodiment. Each of the above information may be determined and signaled by flags, etc. The above prediction features may be performed in S210, and the results of the above prediction and signaling may occur in S211.

[0091] According to an exemplary embodiment, for each vertex in a vertex group in the exemplary flowchart 1300 and the flowchart 1400 described below, after prediction, the residual becomes a 3D displacement vector that indicates the shift from the current vertex to its predictor. The residual of the vertex group needs to be further compressed. In one example, the transformation in S211 can be applied to the residual of the vertex group before entropy coding, together with its signaling. To handle the coding of a group of displacement vectors, the following methods can be implemented. For example, in one method, to properly signal the case where a group of displacement vectors, some displacement vectors, or its components have only zero values. In another embodiment, a flag can be signaled for each displacement vector whether this vector has a non-zero component, and if not, the coding of all components of this displacement vector can be skipped. Furthermore, in another embodiment, a flag can be signaled for each group of displacement vector whether this group has a non-zero vector, and if not, the coding of all displacement vectors of this group can be skipped. Further, in other embodiments, a flag may be signaled for each component of a group of displacement vectors whether this component of the group has any non-zero vectors, and if not, the coding of this component of all displacement vectors of this group may be skipped. Further, in other embodiments, there may be a signaling if a group of displacement vectors or a component of a group of displacement vectors requires a transform, and if not, the transform may be skipped and quantization / entropy coding may be applied directly to the group or group component. Further, in other embodiments, a flag may be signaled for each group of displacement vectors whether this group needs to undergo a transform, and if not, the transform coding of all displacement vectors of this group may be skipped.Furthermore, in other embodiments, a flag is signaled for each component of a group of displacement vectors whether this component of the group needs to undergo a transform, and if not, the transform coding of this component of all displacement vectors of this group can be skipped. The above-mentioned embodiments in this paragraph regarding the processing of vertex prediction residuals may also be combined and performed in parallel, each on a different patch.

[0092] FIG. 14 shows an example flowchart 1400, in which a mesh frame can be coded and obtained as a whole data unit in S221, meaning that all vertices or attributes of the mesh frame may have correlation between them. Alternatively, depending on the decision in S222, the mesh frame can also be divided into smaller independent subpartitions in S223, in a concept similar to slices or tiles of a 2D video or image. The coded mesh frame or the coded mesh subpartition can be assigned a prediction type in S224. Possible prediction types include intra-coding type and inter-coding type. For the intra-coding type, only prediction from a reconstructed part of the same frame or slice is allowed in S225. Meanwhile, the inter-prediction type allows prediction from a previously coded mesh frame in addition to intra-mesh frame prediction in S225. Furthermore, the inter-prediction type can be classified into more subtypes, such as P type and B type. In the P type, only one predictor can be used for prediction purposes, and in the B type, two predictors from two previously coded mesh frames can be used to generate a predictor. A weighted average of two predictors can be an example. If the mesh frame is coded as a whole, the frame can be considered as an intra- or inter-coded mesh frame. For inter-mesh frames, the P or B type can be further identified via signaling. Alternatively, if the mesh frame is coded with further division within the frame, the prediction type assignment of each of the sub-partitions is made in S224. Each of the above information may be determined and signaled by flags or the like, and similar to S210 and S211 of FIG. 13, the features of said prediction may be made in S226, and the result of said prediction and signaling may occur in S227.

[0093] As such, dynamic mesh sequences may require large amounts of data as they may consist of a significant amount of information that changes over time, and efficient compression techniques are required to store and transmit such content, and the above-mentioned features of Figures 20 and 21 represent such improved efficiency by enabling at least improved mesh vertex 3D position prediction by using previously decoded vertices either within the same mesh frame (intra prediction) or from a previously coded mesh frame (inter prediction).

[0094] Further, the exemplary embodiment may generate displacement vectors of the third layer 2303 of the mesh based on one or more of the reconstructed vertices of the second layer 2302 and its previous layer(s), such as the first layer 2301. Assuming that the index of the second layer 2302 is T, predictors of vertices in the third layer 2303T+1 are generated based on at least the reconstructed vertices of the current layer or the second layer 2302. An example of such a layer-based prediction structure is shown in the example 1600 of FIG. 16, which illustrates reconstruction-based vertex prediction, i.e., progressive vertex prediction using edge-based interpolation, where predictors are generated based on previously decoded vertices rather than predictor vertices. The first layer 2301 may be a mesh bounded by a first polygon 2340 having as its vertices the decoded vertices at its boundary and the interpolated vertices along one of the lines between those decoded vertices. As the progressive coding proceeds from the first layer 2301 to the second layer 2302, additional polygons 2341 may be formed by displacement vectors from one of the interpolated vertices of the first layer to additional vertices of the second layer 2302, so that the total number of vertices of the second layer 2302 may be greater than the total number of vertices of the first layer 2301. Similarly, when proceeding to the third layer 2303, the additional vertices of the second layer 2302, together with the decoded vertices from the first layer 2301, may function in the coding in the same way as the decoded vertices functioned when proceeding from the first layer 2301 to the second layer 2303, i.e., multiple additional polygons may be formed. As a note, unlike FIG. 16, example 1900 illustrates that when moving from a first layer 2601 to a second layer 2603 and then to a third layer 2603, each of the additionally formed polygons may be entirely within the polygon formed by the extent of the first layer 2601; see example 1900 in FIG. 19 which illustrates such progressive coding.

[0095] For such an example 1600, since the interpolated vertices of the current layer are predicted values, such values need to be reconstructed before being used to generate predictors for the vertices of the next layer. Refer to the exemplary flowchart 1500 of FIG. 15. This is done by coding the base mesh at S231, performing vertex prediction as such at S232, and then adding the decoded displacement vectors of the current layer to the predictors of the vertices such as layer 2302 at S233. Then, the reconstructed vertices of this layer 2303 can be used to generate and signal the predictor vertices of the next layer 2303 at S235, along with all the decoded vertices of the previous (one or more) layers, such as checking the additional vertex values of such a layer at S234. This process can also be summarized as follows. Let P[t](Vi) represent the predictor of vertex Vi on layer t, R[t](Vi) represent the reconstructed vertex Vi on layer t, D[t](Vi) represent the displacement vector of vertex Vi of layer t, and f(*) represent a predictor generator that can, in particular, be the average of two existing vertices. In that case, according to an exemplary embodiment, for each layer t, the following exists. P[t](Vi)=f(R[s|s<t](Vj), R[m|m<t](Vk)), where Vj and Vk are the reconstructed vertices of the previous layer R[t](Vi)=P[t](Vi)+D[t](Vi) Equation (1)

[0096] Then, for all the vertices of one mesh frame, they are divided into layer 0 (base mesh), layer 1, layer 2, …, etc. In that case, the reconstruction of the vertices on one layer depends on the reconstruction of the vertices on the previous (one or more) layers. Above, each of P, R, and D represents a 3D vector in the context of a 3D mesh representation. D is the decoded displacement vector, and quantization may or may not be applied to this vector.

[0097] According to an exemplary embodiment, vertex prediction using reconstructed vertices may only be applied to certain layers. For example, layer 0 and layer 1. For other layers, vertex prediction can still use nearby predictor vertices without adding displacement vectors to them for reconstruction. Therefore, these other layers can be processed simultaneously without waiting for the previous layer to reconstruct. According to an exemplary embodiment, for each layer, the selection of reconstruction-based vertex prediction or predictor-based vertex prediction can be signaled, or the layer (and subsequent layers) that does not use reconstruction-based vertex prediction can be signaled.

[0098] For displacement vectors generated by vertices whose vertex predictors are reconstructed, quantization can be applied to those displacement vectors without further transformation, such as wavelet transform, etc. For displacement vectors whose vertex predictors are generated by other predictor vertices, a transformation may be required and quantization can be applied to the transform coefficients of those displacement vectors.

[0099] As such, dynamic mesh sequences may require large amounts of data since they may consist of a significant amount of information that changes over time. Therefore, efficient compression techniques are needed to store and transmit such content. In the framework of the interpolation-based vertex prediction method described above, one important step is compressing the displacement vectors, which occupy a major part in the coded bitstream and are the focus of this disclosure, and the features of, for example, FIG. 15, alleviate such problems by providing such compression.

[0100] Furthermore, as with the other examples described above, even in those embodiments, dynamic mesh sequences may still require a large amount of data since they may consist of a significant amount of information that changes over time, and therefore efficient compression techniques are needed to store and transmit such content. In the framework of the 2D atlas sampling based method described above, important advantages may be achieved by inferring connectivity information from sampled vertices and boundary vertices at the decoder side. This is a key part of the decoding process and is the focus of further examples described below.

[0101] According to an example embodiment, the connectivity information of the base mesh can be inferred (derived) from the decoded boundary vertices and sampled vertices for each chart on both the encoder and decoder sides.

[0102] Similar to that described above, any triangulation method can be applied to create connectivity between vertices (including boundary vertices and sampled vertices). For charts without sampling of interior vertices, such as the interior vertices shown in example 1000 of FIG. 10 and example 1800 of FIG. 18 described further below, a similar method of creating connectivity still applies, but according to an example embodiment, the use of different triangulation methods for boundary vertices and sampled vertices may be signaled.

[0103] For example, according to an exemplary embodiment, for every four neighboring points at any sampled location, it may be determined whether the number of occupied points is three or more (examples of occupied or unoccupied points are highlighted in FIG. 18 showing an example occupancy map 1800 where each circle represents an integer pixel), and the triangular connectivity between the four points can be inferred by a certain rule. For example, as illustrated in example 1700 of FIG. 17, in the case of the illustrated examples (2), (3), (4), (4) where three of the four points are determined to be occupied, the points can be directly interconnected to form a triangle as in those examples, whereas, if all four points are determined to be occupied, the points are used to form two triangles as shown in example (1) of FIG. 17. It should be noted that different rules can be applied to different numbers of neighboring points. This process can be performed across many points, as further illustrated in FIG. 18. In this embodiment, the reconstructed mesh is a triangular mesh such as that of FIG. 17, and also a regular triangular mesh in at least the interior portion of FIG. 18, which may not be determined to be signaled according to such regularity, but may instead be coded and decoded as surrounding irregular triangles that should be signaled separately, by inference rather than by separate signaling.

[0104] Also, in an attempt to further reduce complexity and data processing, such a regular interior triangular quad mesh as shown in FIG. 18 could be inferred as such a quad mesh of example (1) of FIG. 17, thereby even reducing the amount of complexity from inferring interior regular triangles to inferring a reduced number of interior regular quad meshes instead.

[0105] According to an example embodiment, a quadrilateral mesh may be reconstructed when all four neighboring points are determined to be occupied, as in example (1) of FIG.

[0106] Inferring from the above description, it is illustrated that the reconstructed mesh in example 1800, as shown in FIG. 18, may be of hybrid type, i.e., some regions within the mesh frame generate triangular meshes and other regions generate quadrilateral meshes, some of said triangular meshes being regular compared to other triangular meshes therein, and some being irregular, such as boundary triangular meshes but not necessarily all such meshes being on the boundary.

[0107] According to an example embodiment, such connectivity type can be signaled in a high level syntax such as a sequence header or slice header.

[0108] As mentioned above, connectivity information can also be reconstructed by explicit signaling, such as in the case of irregularly shaped triangular meshes. That is, if it is determined that a polygon cannot be reconstructed by implicit rules, the encoder can signal connectivity information in the bitstream. Also, according to an exemplary embodiment, the overhead of such explicit signaling can be reduced depending on the polygon boundary. For example, as shown in the example 1800 of FIG. 18, the connectivity information of triangles is to be signaled to be reconstructed by both implicit rules, such as according to the regular example 2400 of FIG. 17 that can be inferred, and explicit signaling, at least for irregularly shaped polygons shown on the mesh boundary in FIG. 18.

[0109] According to an embodiment, it is decided that only connectivity information between boundary vertices and sampled locations is signaled; connectivity information between the sampled locations themselves is inferred.

[0110] Also, in any of the embodiments, connectivity information can be signaled predictively, such that only the difference between the estimated connectivity (as a prediction) from one mesh to another can be signaled in the bitstream.

[0111] As a note, the inferred triangle orientation (e.g., inferred clockwise or counterclockwise for each triangle) can be signaled for all charts in a high-level syntax such as sequence header, slice header, etc., or fixed (assumed) by the encoder and decoder, according to an example embodiment. The inferred triangle orientation can also be signaled differently for each chart.

[0112] As a further note, any reconstructed mesh may have a different connectivity than the original mesh, for example, the original mesh may be a triangle mesh, while the reconstructed mesh may be a polygon mesh (e.g., a quad mesh).

[0113] According to an exemplary embodiment, the connectivity information of any base vertices may not be signaled, and instead the edges between the base vertices may be derived using the same algorithm at both the encoder and decoder side. See, for example, how the bottom vertices of example 1800 are all occupied, and thus the coding may utilize such information by inferring later, thus determining that such vertices are occupied as bases, thereby the connectivity information of any base vertices may not be signaled, and instead the edges between the base vertices may be derived using the same algorithm at both the encoder and decoder side. Also, according to an exemplary embodiment, the predicted vertex interpolation for additional mesh vertices may be based on the derived edges of the base mesh.

[0114] According to an example embodiment, a flag may be used to signal whether the connectivity information of the base vertices should be signaled or derived, and such a flag can be signaled at different levels of the bitstream, such as the sequence level, the frame level, etc.

[0115] According to an exemplary embodiment, the edges between the base vertices are first derived using the same algorithm on both the encoder and decoder sides. Then, the difference between the derived edges and the actual edges is signaled compared with the original connectivity of the base mesh vertices. Thus, after decoding the difference, the original connectivity of the base vertices can be restored.

[0116] In one example, for derived edges, if they are determined to be erroneous when compared to the original edges, such information may be signaled in the bitstream (by indicating the pair of vertices that form this edge), and for original edges, if they are not derived, they may be signaled in the bitstream (by indicating the pair of vertices that form this edge). Furthermore, connectivity on and vertex interpolation involving boundary edges may be performed separately from interior vertices and edges.

[0117] Thus, by the exemplary embodiments described herein, the technical problems described above may be advantageously ameliorated by one or more of these technical solutions. For example, dynamic mesh sequences may require large amounts of data, as they may consist of a significant amount of information that changes over time, and therefore the exemplary embodiments described herein represent at least an efficient compression technique for storing and transmitting such content.

[0118] The above-described embodiment may further be applied to instance-based mesh coding, where an instance may be a mesh of an object or a part of an object. For example, the illustrative example 2100 of FIG. 21 shows an example mesh 2801 in which various instances 2802 (representing a mesh of a cup), 2803 (representing a mesh of a spoon), and 2804 (representing a mesh of a plate) exist and may be separated and coded. Also, each of the instances 2801, 2802, 2803, 2804 are illustrated within respective bounding boxes, which will be described further below, but it should be noted that the instance 2801 may be considered to be illustrated as being surrounded by a "mesh-based bounding box", while each of the instances 2802, 2803, 2804 may be considered to be surrounded by a respective "instance-based bounding box".

[0119] According to an exemplary embodiment, the proposed methods may be used separately or combined in any order. Although only triangular meshes were used to demonstrate the various embodiments, the proposed methods may be used for any polygon mesh. As mentioned above, it is assumed that an input mesh may contain one or more instances, and a sub-mesh is a portion of an input mesh that has one or more instances, and multiple instances may be grouped to form a sub-mesh.

[0120] In that regard, Figure 20 illustrates an example 2000 in which it is proposed to separately quantize different objects or parts at a given input bit depth (which bit depth may be referred to as "QP"). For example, at 2701, one or more input meshes may be obtained and each separated into a number of sub-meshes. The sub-meshes may be objects, instances of objects, or segmented regions, which according to an exemplary embodiment are independently quantized at S2702.

[0121] According to an example embodiment, a mesh M having m points at (x, y, z) coordinates may be quantized by the QP bit depth in S2702. The quantization step size in all three dimensions (x, y, z) is the maximum length d of the bounding box in all dimensions. bbox >0. Also, the same quantization step size may be applied in S2704 to all objects in the mesh identified in S2703, as follows:

number

number

number

number

number

[0122] However, in complex scenes, the largest objects are often the background, which is relatively simple and can tolerate a higher quantization step size, while the main objects are smaller and suffer from large quantization errors that can be accounted for by various embodiments described further below.

[0123] Therefore, as shown in the example 2200 of FIG. 22, the bounding box d bbox The maximum length of is always the bounding box of each instance:

number

number

number

[0124] For a given bit depth QP, the quantization step size of each of all the instances, instance 2802 (representing a mesh of a cup), instance 2803 (representing a mesh of a spoon), and instance 2804 (representing a mesh of a plate), is always

number

[0125] Therefore, the quantization error per instance is smaller, thus reducing the overall quantization error.

[0126] According to various embodiments, the bit depth may be adaptively assigned to each instance / region, called a "sub-mesh" in S2902, and may be determined based on the areal density of that particular instance. Each sub-mesh may be obtained from the volumetric data of the mesh, which itself may signal each instance in the mesh individually, and each sub-mesh is derived from that mesh on an instance-by-instance basis in S2902. For example, each of the instances 2802, 2803, 2804 may be assigned its own respective bit depth in S2904 according to its own particular areal density, or the number of vertices forming one or more of the aforementioned polygons therein. In general, the more faces each instance has, which may be determined by counting the number of such polygons therein, etc., in S2903, the less quantization should be applied to that instance in S2702. For example, given a mesh M, the total number of faces is n, and the corresponding faces of sub-mesh k are:

number

number

number

number

[0127] According to various embodiments, the meshes are represented as a base mesh B and its corresponding displacement D, which are quantized at different bit depths in S2702. For example, for the kth object, the bit depths of the base mesh B and its corresponding displacement D are

number

number

number

[0128] According to various embodiments, an adaptive bit depth parameter based on minimizing distortion may be used. For example, given an input bit depth QP, the mean square error (MSE) of the quantization method may be ∈_QP, as in equation (4). The MSE of each sub-mesh is derived as ∈_QP̂k=ω_k*ε_QP, ∀k∈[1,...,K], where ω_k>0 is a weighting factor. In one example, ω_k=1∀k. A linear search may be performed:

number

[0129] Additionally, the best bit depth for displacement is

number

[0130] According to an example embodiment, there may be signaling of the quantization of each object, such as by signaling via the S2907 bitstream. The set of ascending base quantization bit depths is

number

number

[0131] [Table 1]

[0132] In the table, u(n) is an unsigned integer using n bits, i(n) is an integer using n bits, mips_quant() is a sequence of signaling data, mips_min_bbox[k] is the minimum of the bounding box in the i-dimension, mips_num_instances_minus1 is the number of instances in the mesh minus 1, mips_base_bitdepth_minus1 is the bit depth of the first instance in this sequence, mips_base_quant[k] is the difference between the quantization of the (k+1)th and the kth submesh. The quantization set is sorted in ascending order, so this number is always non-negative. mips_dist_quant[k] is the kth quantization data of the bit depth of the base mesh.

[0133] According to various embodiments, to reduce signaling overhead, multiple instances may be grouped into K groups with the same bit depth. The instances are clustered into bounding boxes using a simple clustering method such as K-means clustering.

number

[0134] The techniques described above can be implemented as computer software physically stored on one or more computer readable media using computer readable instructions, or by one or more specifically configured hardware processors. For example, Figure 23 illustrates a computer system 2300 suitable for implementing certain embodiments of the disclosed subject matter.

[0135] The computer software can be coded using any suitable machine code or computer language that can be subjected to mechanisms such as assembly, compilation, linking, etc. to create code containing instructions that can be executed directly by a computer central processing unit (CPU), graphics processing unit (GPU), etc., or via interpretation, microcode execution, etc.

[0136] The instructions may be executed on various types of computers or computer components including, for example, personal computers, tablet computers, servers, smartphones, gaming consoles, Internet of Things devices, and the like.

[0137] 23 for computer system 2300 are exemplary in nature and are not intended to suggest any limitation as to the scope of use or functionality of the computer software implementing the embodiments of the present disclosure. Nor should the arrangement of components be interpreted as having a dependency or requirement regarding any one or combination of components illustrated in the exemplary embodiment of computer system 2300.

[0138] The computer system 2300 may include certain human interface input devices. Such human interface input devices may be responsive to input by one or more human users via, for example, tactile input (e.g., keystrokes, swipes, data glove movements), audio input (e.g., voice, clapping), visual input (e.g., gestures), olfactory input (not shown). The human interface devices may also be used to capture certain media not necessarily directly associated with conscious human input, such as audio (e.g., voice, music, ambient sounds), images (e.g., scanned images, photographic images obtained from still image cameras), video (two-dimensional video, three-dimensional video including stereoscopic video, etc.).

[0139] The input human interface devices may include one or more of a keyboard 2301, a mouse 2302, a trackpad 2303, a touch screen 2310, a joystick 2305, a microphone 2306, a scanner 2308, a camera 2307 (only one of each is shown).

[0140] The computer system 2300 may also include certain human interface output devices. Such human interface output devices may stimulate one or more of the senses of a human user, for example, through haptic output, sound, light, and smell / taste. Such human interface output devices may include haptic output devices (e.g., haptic feedback via touch screen 2310 or joystick 2305, although there may also be haptic feedback devices that do not function as input devices), audio output devices (e.g., speakers 2309, headphones (not shown)), visual output devices (e.g., screens 2310 including CRT screens, LCD screens, plasma screens, OLED screens, each with or without touch screen input capability, each with or without haptic feedback capability, some of which may be capable of outputting two-dimensional visual output or output in more than three dimensions via means such as stereoscopic output, virtual reality glasses (not shown), holographic displays, and smoke tanks (not shown)), and printers (not shown).

[0141] The computer system 2300 may also include human accessible storage devices and their associated media, such as optical media including a CD / DVD ROM / RW 2320 having media such as CD / DVD 2311, a thumb drive 2322, a removable hard drive or solid state drive 2323, legacy magnetic media such as tape or floppy disks (not shown), dedicated ROM / ASIC / PLD based devices such as security dongles (not shown), etc.

[0142] Those skilled in the art will also understand that the term "computer-readable medium" as used in connection with the subject matter of this disclosure does not encompass transmission media, carrier waves, or other transitory signals.

[0143] The computer system 2300 may also include an interface 2399 to one or more communications networks 2398. The networks 2398 may be, for example, wireless, wired, optical. The networks 2398 may further be local, wide area, metropolitan, vehicular and industrial, real-time, delay tolerant, etc. Examples of networks 2398 include local area networks such as Ethernet, WLAN, etc., cellular networks including GSM, 3G, 4G, 5G, LTE, etc., television wired or wireless wide area digital networks including cable television, satellite television, and terrestrial broadcast television, vehicular and industrial including CANBus, etc. Specific networks 2398 generally require an external network interface adapter attached to a specific general-purpose data port or peripheral bus (2350 and 2351) (e.g., a USB port of the computer system 2300, etc.), while other networks are generally built into the core of the computer system 2300 by connection to the system bus as described below (e.g., an Ethernet interface to a PC computer system or a cellular network interface to a smartphone computer system). Using any of these networks 2398, the computer system 2300 can communicate with other entities. Such communications can be unidirectional receive only (e.g., broadcast television), unidirectional transmit only (e.g., CANbus to certain CANbus devices), or bidirectional to other computer systems using, for example, local or wide area digital networks. Specific protocols and protocol stacks can be used with each of these networks and network interfaces, as described above.

[0144] The aforementioned human interface devices, human accessible storage devices, and network interfaces can be connected to core 2340 of computer system 2300.

[0145] The core 2340 may include one or more central processing units (CPUs) 2341, graphics processing units (GPUs) 2342, graphics adapters 2317, dedicated programmable processing units in the form of field programmable gate areas (FPGAs) 2343, hardware accelerators for specific tasks 2344, etc. These devices may be connected via a system bus 2348 along with read only memory (ROM) 2345, random access memory 2346, internal mass storage such as an internal non-user accessible hard drive, SSD, etc. 2347. In some computer systems, the system bus 2348 may be accessible in the form of one or more physical plugs to allow expansion with additional CPUs, GPUs, etc. Peripheral devices may be connected directly to the core's system bus 2348 or via a peripheral bus 2349. Architectures for peripheral buses include PCI, USB, etc.

[0146] The CPU 2341, GPU 2342, FPGA 2343, and accelerator 2344 can execute certain instructions that may combine to constitute the aforementioned computer code. That computer code may be stored in ROM 2345 or RAM 2346. Persistent data may be stored, for example, in internal mass storage 2347, while temporary data may also be stored in RAM 2346. Rapid storage and retrieval in any of the memory devices may be made possible by the use of cache memories that may be closely associated with one or more of the CPU 2341, GPU 2342, mass storage 2347, ROM 2345, RAM 2346, etc.

[0147] The computer-readable medium can bear computer code for performing various computer-implemented operations. The medium and computer code can be those specially designed and constructed for the purposes of the present disclosure, or they can be of the available kind well known to those skilled in the computer software arts.

[0148] By way of example and not limitation, computer system 2300 having the architecture, and specifically core 2340, may provide functionality as a result of processor(s) (including CPU, GPU, FPGA, accelerator, etc.) executing software embodied in one or more tangible computer-readable media. Such computer-readable media may be user-accessible mass storage devices as described above, as well as media associated with specific storage of core 2340 of a non-transitory nature, such as core internal mass storage 2347 and ROM 2345. Software implementing various embodiments of the present disclosure may be stored in such devices and executed by core 2340. Computer-readable media may include one or more memory devices or chips, depending on the particular needs. The software may cause core 2340, and specifically the processors therein (including CPU, GPU, FPGA, etc.) to perform certain processes or certain portions of certain processes described herein, including defining data structures stored in RAM 2346 and modifying such data structures according to the processes defined by the software. Additionally or alternatively, the computer system may provide functionality as a result of logic hardwired or otherwise embodied in circuitry (e.g., accelerator 2344), which may operate in place of or in conjunction with software to perform particular processes or particular portions of particular processes described herein. References to software may encompass logic, where appropriate, and vice versa. References to computer-readable media may encompass circuitry (such as integrated circuits (ICs)) that stores software for execution, circuitry that embodies logic for execution, or both, where appropriate. The present disclosure encompasses any suitable combination of hardware and software.

[0149] While this disclosure describes several exemplary embodiments, there are alterations, permutations, and various alternative equivalents that fall within the scope of this disclosure. Thus, it will be appreciated that those skilled in the art will be able to devise numerous systems and methods that, although not explicitly shown or described herein, embody the principles of the present disclosure and are thus within its spirit and scope. [Explanation of symbols]

[0150] 100 Communication Systems Terminals 101-104 105 Network 201 Video Sources 202 Encoder 203 Capture Subsystem 204 encoded video bitstream 205 Streaming Server 206 Copying the encoded video bitstream 207 Streaming Client 208 Copying the encoded video bitstream 209 Display 210 Output video sample stream 211 Video Decoder 212 Streaming Client 213 Uncompressed Video Sample Stream 300 Decoder 301 Channel 302 Receiver 303 Buffer Memory 304 Parser 305 Scaler / Descaler Unit 306 Motion Compensation Prediction Unit 307 Intra Prediction Units 308 Reference Picture Buffer 309 Current Picture 310 Aggregator 311 Loop Filter 312 Display 313 Symbols 400 Encoder 401 Source 402 Controller 403 Source Coder 404 Predictor 405 Reference Picture Memory 406 Decoder 407 Coding Engine 408 Entropy Coder 409 Transmitter 410 coded video sequence 411 Channel 500 Workflow Diagram 600 Content Flow Process Diagram 700 in 1 dynamic mesh compression framework 800 Volumetric Data Examples 900 Examples 1001 Acquired Block 1002 Audio Encoding Block 1003 Processing Block 1004 Video Encoding Block 1005 Image Encoding Block 1007 Delivery Block 1008 Head / Eye Tracking Block 1000 Examples 1010 Audio Decode Block 1011 Audio Rendering Block 1012 Speaker / headphone block 1013 Video Decoding Block 1014 Image Decoding Block 1015 Image Rendering Block 1016 Display Block 1020 OMAF Player 1100 Examples 1101 Volumetric Data Acquisition Block 1102 Point Cloud Block 1103 Image Block 1104 Video Encoding Block 1105 Image Encoding Block 1106 File / Segment Encapsulation Block 1107 Cloud Server Block 1108 Position / Field of View Tracking Block 1109 Scene Generator Block 1112 Point Cloud Reconstruction Block 1113 Scene building blocks 1114 Display Block 1125 V-PCC Player 1200 Examples 1201 Input Mesh 1202 2D UV Atlas 1203 Decoder 1204 Reconstructed Mesh 1300 Exemplary Flowchart 1301 3D Mesh Segments 1302 UV Parameterization Process 1303 2D Chart 1304 2D UV Atlas 1400 Exemplary Flowchart 1401, 1402 2D Chart 1500 Exemplary Flowchart 1600~1800 examples 1801 Solid Triangle 1802 dashed point 1803 Newly decoded vertices 1900 examples Mesh frames coded before 1901 1902 Mesh Frame 2100 Examples 2301 First Layer 2302 Second Layer 2303 Third Layer 2340 First Polygon 2341 additional polygons 2601 First Layer 2602 Second Layer 2603 Third Layer 2801 Mesh example 2802 instances representing the mesh of a cup 2803 instances representing the spoon mesh 2804 instances representing the mesh of a plate

Claims

1. 1. A method for video coding, the method being performed by at least one processor, comprising: obtaining an input mesh comprising volumetric data for at least one three-dimensional (3D) visual content; deriving a plurality of sub-meshes of the input mesh from the frame of volumetric data, each of the sub-meshes including a respective one of the instances of the object, and at least a first sub-mesh and a second sub-mesh from the plurality of the sub-meshes overlap each other in the frame; setting a first bit depth for the first sub-mesh and a second bit depth for the second sub-mesh, the first bit depth being different from the second bit depth; quantizing the first sub-mesh and the second sub-mesh based on the first bit-depth and the second bit-depth, respectively; signaling the result of quantizing the first sub-mesh and the second sub-mesh; 23. A method for video coding comprising:

2. the volumetric data includes the first sub-mesh and the second sub-mesh overlapping each other and bounded by a bounding box; deriving the plurality of sub-meshes includes enclosing each of the instances of the object with a respective second bounding box; At either the first bit depth or the second bit depth, a quantization step size of either the first submesh or the second submesh is smaller than a quantization step size of the first submesh and the second submesh that overlap each other and are enclosed by the bounding box. A method for video coding according to claim 1.

3. setting the first bit depth based on determining a first areal density of the first sub-mesh; setting the second bit depth is based on determining a second areal density of the second sub-mesh; A method for video coding according to claim 2.

4. quantizing the first sub-mesh and the second sub-mesh includes: applying a first level of quantization to the first sub-mesh based on the first bit depth; applying a second level of quantization to the second submesh based on the second bit depth; the first level is set to be lower than the second level based on determining that the first bit depth indicates that the first sub-mesh has one of the areal densities greater than that indicated by the second bit depth set for the second sub-mesh. A method for video coding according to claim 3.

5. the first sub-mesh is bounded by a first of the second bounding boxes; the second sub-mesh is bounded by a second one of the second bounding boxes; determining the first and second areal densities includes comparing a number of faces of the first sub-mesh and the second sub-mesh to a volume of the first one of the second bounding boxes and the second one of the second bounding boxes, respectively; A method for video coding according to claim 3.

6. signaling the result of quantizing the first submesh and the second submesh includes signaling that each of the first submesh and the second submesh share the same bounding box offset. A method for video coding according to claim 2.

7. signaling the result of quantizing the first sub-mesh and the second sub-mesh includes signaling a total number of the instances of the object in the frame. A method for video coding according to claim 1.

8. signaling the results of quantizing the first submesh and the second submesh includes signaling a difference between the quantizations applied to the first submesh and the second submesh and sorting the difference compared to other quantizations applied to other submeshes of the frame. A method for video coding according to claim 1.

9. the first bit depth is applied to at least one other sub-mesh of the other sub-meshes; signaling the result of quantizing the first submesh and the second submesh includes grouping the first submesh with the at least one other submesh of the other submeshes based on determining that the first bit depth applies to both the first submesh and the at least one other submesh of the other submeshes; A method for video coding according to claim 8.

10. wherein the step of setting the first bit depth and the second bit depth includes the step of deriving a mean square error for each of the first sub-mesh and the second sub-mesh at each of the first bit depth and the second bit depth. A method for video coding according to claim 1.

11. 1. An apparatus for video coding, comprising: at least one memory configured to store computer program code; at least one processor configured to access the computer program code and to operate as instructed by the computer program code, the computer program code comprising: obtaining code configured to cause the at least one processor to obtain an input mesh comprising volumetric data of at least one three-dimensional (3D) visual content; derivation code configured to cause the at least one processor to derive a plurality of sub-meshes of the input mesh from the frame of the volumetric data, each of the sub-meshes including a respective one of the instances of the object, and a first sub-mesh and a second sub-mesh from the plurality of sub-meshes overlap each other in the frame; and setting code configured to cause the at least one processor to set a first bit depth for the first submesh and a second bit depth for the second submesh, the first bit depth being different from the second bit depth; quantization code configured to cause the at least one processor to quantize the first sub-mesh and the second sub-mesh based on the first bit-depth and the second bit-depth, respectively; signaling code configured to cause the at least one processor to signal a result of quantizing the first sub-mesh and the second sub-mesh; At least one processor, 23. An apparatus for video coding comprising:

12. the volumetric data includes the first sub-mesh and the second sub-mesh overlapping each other and bounded by a bounding box; deriving the plurality of sub-meshes includes enclosing each of the instances of the object with a respective second bounding box; At either the first bit depth or the second bit depth, a quantization step size of either the first submesh or the second submesh is smaller than a quantization step size of the first submesh and the second submesh that overlap each other and are enclosed by the bounding box. An apparatus for video coding according to claim 11.

13. setting the first bit depth based on determining a first areal density of the first sub-mesh; setting the second bit depth is based on determining a second areal density of the second sub-mesh; An apparatus for video coding according to claim 12.

14. Quantizing the at least two of the sub-meshes includes: applying a first level of quantization to the first submesh based on the first bit depth; applying a second level of quantization to the second submesh based on the second bit depth; the first level is set to be lower than the second level based on determining that the first bit depth indicates that the first sub-mesh has one of the areal densities greater than that indicated by the second bit depth set for the second sub-mesh. An apparatus for video coding according to claim 13.

15. the first sub-mesh is bounded by a first of the second bounding boxes; the second sub-mesh is bounded by a second one of the second bounding boxes; determining the first and second areal densities includes comparing a number of faces of the first sub-mesh and the second sub-mesh to a volume of the first one of the second bounding boxes and the second one of the second bounding boxes, respectively; An apparatus for video coding according to claim 13.

16. signaling the result of quantizing the first submesh and the second submesh includes signaling that each of the first submesh and the second submesh share the same bounding box offset. An apparatus for video coding according to claim 12.

17. signaling the result of quantizing the first sub-mesh and the second sub-mesh includes signaling a total number of the instances of the object within the frame. An apparatus for video coding according to claim 11.

18. signaling the results of quantizing the first submesh and the second submesh includes signaling a difference between the quantizations applied to the first submesh and the second submesh and sorting the difference compared to other quantizations applied to other submeshes of the frame.

12. An apparatus for video coding according to claim 11.

19. the first bit depth is applied to at least one other sub-mesh of the other sub-meshes; signaling the result of quantizing the first submesh and the second submesh includes grouping the first submesh of the first submesh and the second submesh with the at least one other submesh of the other submeshes based on determining that the first bit depth applies to both the first submesh and the at least one other submesh of the other submeshes. An apparatus for video coding according to claim 18.

20. On the computer, obtaining an input mesh including volumetric data for at least one three-dimensional (3D) visual content; deriving a plurality of sub-meshes of the input mesh from the frame of volumetric data, each of the sub-meshes including a respective one of the instances of the object, and at least a first sub-mesh and a second sub-mesh from the plurality of sub-meshes overlap each other in the frame; setting a first bit depth for the first sub-mesh and a second bit depth for the second sub-mesh, the first bit depth being different from the second bit depth; quantizing the first sub-mesh and the second sub-mesh based on the first bit-depth and the second bit-depth, respectively; signaling a result of quantizing the first sub-mesh and the second sub-mesh; A non-transitory computer-readable medium storing a program.

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