Mesh data encoding device, mesh data encoding method, mesh data decoding device, and mesh data decoding method

Abstract

A decoding method according to embodiments may comprise the steps of: decoding a base mesh in a bitstream; decoding a displacement in the bitstream; and decoding an attribute in the bitstream. An encoding method according to embodiments may comprise the steps of: encoding a base mesh of mesh data; encoding a displacement of the mesh data; and encoding an attribute of the mesh data.

Description

Mesh data encoding device, mesh data encoding method, mesh data decoding device, and mesh data decoding method

[0001] The embodiments provide a method for providing Point Cloud content to provide users with various services such as Virtual Reality (VR), Augmented Reality (AR), Mixed Reality (MR), and autonomous driving services.

[0002] A point cloud is a collection of points in 3D space. The sheer number of points in 3D space makes it difficult to generate point cloud data.

[0003] There is a problem that a lot of processing power is required to transmit and receive point cloud data.

[0004] The technical problem according to the embodiments is to provide a point cloud data transmission device, transmission method, point cloud data reception device and reception method for efficiently transmitting and receiving point clouds in order to solve the problems described above.

[0005] The technical problem according to the embodiments is to provide a point cloud data transmission device, transmission method, point cloud data reception device, and reception method for resolving latency and encoding / decoding complexity.

[0006] However, the scope of the embodiments is not limited to the aforementioned technical tasks, and the scope of the embodiments may be expanded to other technical tasks that can be inferred by a person skilled in the art based on the entire contents of this document.

[0007] To achieve the above-described purpose and other advantages, a decoding method according to embodiments may include a step of decoding a base mesh in a bitstream; a step of decoding a displacement in the bitstream; and a step of decoding an attribute in the bitstream. An encoding method according to embodiments may include a step of encoding a base mesh of mesh data; a step of encoding a displacement of the mesh data; and a step of encoding an attribute of the mesh data.

[0008] The point cloud data transmission method, transmission device, point cloud data reception method, and reception device according to the embodiments can provide a high-quality point cloud service.

[0009] The point cloud data transmission method, transmission device, point cloud data reception method, and reception device according to the embodiments can achieve various video codec methods.

[0010] The point cloud data transmission method, transmission device, point cloud data reception method, and reception device according to the embodiments can provide general-purpose point cloud content such as autonomous driving services.

[0011] The drawings are included to further understand the embodiments, and the drawings illustrate the embodiments together with the description related to the embodiments. For a better understanding of the various embodiments described below, reference should be made to the following description of the embodiments in conjunction with the following drawings, in which like reference numerals correspond to corresponding parts throughout the drawings.

[0012] Figure 1 illustrates a system for providing dynamic mesh content according to embodiments.

[0013] Figure 2 illustrates a V-MESH compression method according to embodiments.

[0014] Figure 3 illustrates pre-processing of V-MESH compression according to embodiments.

[0015] Figure 4 illustrates a mid-edge subdivision method according to embodiments.

[0016] Figure 5 shows a displacement generation process according to embodiments.

[0017] FIG. 6 illustrates an intra-frame encoding process of a V-MESH compression method according to embodiments.

[0018] Figure 7 illustrates an inter-frame encoding process of a V-MESH compression method according to embodiments.

[0019] Figure 8 shows a lifting conversion process for displacement according to embodiments.

[0020] Figure 9 illustrates a process of packing transformation coefficients according to embodiments into a 2D image.

[0021] Fig. 10 shows an attribute transfer process of a V-MESH compression method according to embodiments.

[0022] Fig. 11 illustrates an intra-frame decoding process of a V-MESH compression method according to embodiments.

[0023] Fig. 12 shows a V-MES and Fig. 13 shows a point cloud data transmission device according to embodiments.

[0024] Fig. 13 shows a point cloud data transmission device according to embodiments.

[0025] Fig. 14 shows a point cloud data receiving device according to embodiments.

[0026] Figure 15 shows a bitstream according to embodiments.

[0027] Figure 16 shows the payload of the V3C unit according to embodiments.

[0028] Fig. 17 shows an encoder according to embodiments.

[0029] Figure 18 shows displacement vector encoding according to embodiments.

[0030] Figures 19 and 20 illustrate examples of designating a quantized displacement vector transform coefficient packing area for each LoD according to embodiments as MCTS.

[0031] Figure 21 shows an example of specifying a quantized displacement vector transform coefficient packing area for each LoD according to embodiments.

[0032] Figure 22 shows an example of specifying a quantized displacement vector transform coefficient packing area for each LoD according to embodiments.

[0033] Figure 23 shows displacement vector transform according to embodiments.

[0034] Figure 24 shows a lifting-based displacement vector transform according to embodiments.

[0035] Fig. 25 shows a decoder according to embodiments.

[0036] Figure 26 shows the displacement vector coordinate system inverse transformation and normal vector derivation according to embodiments.

[0037] Figure 27 shows displacement vector decoding according to embodiments.

[0038] Figure 28 shows a lifting-based displacement vector inverse transform according to embodiments.

[0039] Figure 29 shows geometry information syntax according to embodiments.

[0040] FIG. 30 illustrates a displacement partial extraction SEI payload syntax according to embodiments.

[0041] Figure 31 shows the LoD extraction information SEI payload syntax according to embodiments.

[0042] Fig. 32 shows a decoder according to embodiments.

[0043] Figure 33 shows the relationship between refinement level and packing of frame areas according to embodiments.

[0044] Figure 34 shows an example of the configuration and signaling of a LoD star area according to embodiments.

[0045] Figure 35 shows an example of the configuration and signaling of areas by refinement level according to embodiments.

[0046] Figure 36 shows an encoding method according to embodiments.

[0047] Figure 37 shows a decryption method according to embodiments.

[0048] Preferred embodiments of the embodiments are described in detail, examples of which are illustrated in the accompanying drawings. The following detailed description, with reference to the accompanying drawings, is intended to illustrate preferred embodiments of the embodiments, rather than merely show embodiments that can be implemented according to the embodiments. The following detailed description includes details to provide a thorough understanding of the embodiments. However, it will be apparent to those skilled in the art that the embodiments may be practiced without these details.

[0049] While most of the terms used in the examples are commonly used in the field, some terms were arbitrarily selected by the applicant, and their meanings are described in detail in the following descriptions as needed. Therefore, the examples should be understood based on the intended meaning of the terms, not simply their names or meanings.

[0050] Figure 1 illustrates a system for providing dynamic mesh content according to embodiments.

[0051] The system of FIG. 1 includes a point cloud data transmission device (100) and a point cloud data reception device (110) according to embodiments. The point cloud data transmission device may include a dynamic mesh video acquisition unit (101), a dynamic mesh video encoder (102), a file / segment encapsulator (103), and a transmitter (104). The point cloud data reception device (110) may include a reception unit (111), a file / segment decapsulator (112), a dynamic mesh video decoder (113), and a renderer (114). Each component of FIG. 1 may correspond to hardware, software, a processor, and / or a combination thereof. Hereinafter, the point cloud data transmission device according to embodiments may be interpreted as a term referring to the transmission device (100) or a dynamic mesh video encoder (hereinafter, referred to as an encoder) (102). The point cloud data receiving device according to the embodiments may be interpreted as a term referring to a receiving device (110) or a dynamic mesh video decoder (hereinafter, decoder) (113).

[0052] The system of Fig. 1 can perform video-based dynamic mesh compression and decompression.

[0053] Advances in 3D capture, modeling, and rendering have enabled users to consume diverse forms of 3D content, such as AR, XR, metaverse, and holograms, across multiple platforms and devices. 3D content increasingly represents objects with greater precision and realism, enabling users to enjoy immersive experiences. To achieve this, the creation and use of 3D models requires a significant amount of data. Among various types of 3D content, 3D meshes are widely used for efficient data utilization and realistic object representation. Embodiments include a series of processing steps in a system that utilizes such mesh content.

[0054] First, the method of compressing dynamic mesh data starts with the V-PCC (Video-based point cloud compression) standard technology. Point cloud data is data that contains color information at the vertex coordinates (X, Y, Z). Mesh data refers to data in which connectivity information between vertices is added to this vertex information. When creating content, it can be created in the form of mesh data from the beginning. By adding connectivity information to point cloud data, it can be converted into mesh data and used.

[0055] Currently, the MPEG standards body defines two types of dynamic mesh data: Category 1: Mesh data with texture maps as color information. Category 2: Mesh data with vertex colors as color information.

[0056] Mesh coding standards for Category 1 data are currently under development, and work on Category 2 data standards is also planned for the future. The overall process for providing mesh content services may include acquisition, encoding, transmission, decoding, rendering, and / or feedback, as shown in Figure 1.

[0057] To provide mesh content services, 3D data acquired through multiple cameras or specialized cameras can be processed into mesh data types through a series of processes and then converted into video. The generated mesh video is then transmitted through a series of processes, and the receiving end can then reprocess the received data into mesh video and render it. This allows mesh video to be presented to users, who can then interact with the mesh content according to their intended intent.

[0058] A mesh compression system may include a transmitting device and a receiving device. The transmitting device can encode mesh video to output a bitstream, which can be delivered to the receiving device via digital storage media or a network in the form of a file or streaming segment. The digital storage media may include various storage media, such as USB, SD, CD, DVD, Blu-ray, HDD, or SSD.

[0059] The transmitting device may roughly include a mesh video acquisition unit, a mesh video encoder, and a transmitting unit. The receiving device may roughly include a receiving unit, a mesh video decoder, and a renderer. The encoder may be referred to as a mesh video / video / picture / frame encoding device, and the decoder may be referred to as a mesh video / video / picture / frame decoding device. The transmitter may be included in the mesh video encoder. The receiver may be included in the mesh video decoder. The renderer may include a display unit, and the renderer and / or the display unit may be configured as separate devices or external components. The transmitting device and the receiving device may further include separate internal or external modules / units / components for a feedback process.

[0060] Mesh data represents the surface of an object as a number of polygons. Each polygon is defined by its vertices in 3D space and connection information that describes how those vertices are connected. It can also contain vertex properties such as vertex color and normal. Mapping information that allows the surface of the mesh to be mapped to a 2D planar area can also be included as a mesh property. The mapping is typically described as a set of parametric coordinates, called UV coordinates or texture coordinates, associated with the mesh vertices. Meshes contain 2D attribute maps, which can be used to store high-resolution attribute information such as textures, normals, and displacement.

[0061] The mesh video acquisition unit may include processing 3D object data acquired through a camera, etc. into a mesh data type with the properties described above through a series of processes and generating a video composed of such mesh data. The mesh video may have properties of the mesh, such as vertices, polygons, connection information between vertices, colors, normals, etc., that may change over time. A mesh video with properties and connection information that change over time can be expressed as a dynamic mesh video.

[0062] A mesh video encoder can encode an input mesh video into one or more video streams. A single video can include multiple frames, and a single frame can correspond to a still image / picture. In this document, a mesh video can include a mesh image / frame / picture, and the mesh video can be used interchangeably with the mesh image / frame / picture. A mesh video encoder can perform a Video-based Dynamic Mesh (V-Mesh) Compression procedure. A mesh video encoder can perform a series of procedures such as prediction, transformation, quantization, and entropy coding for compression and coding efficiency. The encoded data (encoded video / image information) can be output in the form of a bitstream.

[0063] The encapsulation processing unit (file / segment encapsulation module) can encapsulate encoded mesh video data and / or mesh video-related metadata in the form of a file, etc. Here, the mesh video-related metadata may be received from the metadata processing unit, etc. The metadata processing unit may be included in the mesh video encoder, or may be configured as a separate component / module. The encapsulation processing unit may encapsulate the corresponding data in a file format such as ISOBMFF, or process it in the form of other DASH segments, etc. The encapsulation processing unit may include mesh video-related metadata in the file format according to an embodiment. The mesh video metadata may be included in boxes at various levels in the ISOBMFF file format, for example, or may be included as data in a separate track within the file. According to an embodiment, the encapsulation processing unit may encapsulate mesh video-related metadata itself in a file.

[0064] The transmission processing unit can process encapsulated mesh video data for transmission according to the file format. The transmission processing unit can be included in the transmission unit, or can be configured as a separate component / module. The transmission processing unit can process mesh video data according to any transmission protocol. The processing for transmission can include processing for transmission through a broadcast network or processing for transmission through broadband. According to an embodiment, the transmission processing unit can receive not only mesh video data but also mesh video-related metadata from the metadata processing unit and process the same for transmission.

[0065] The transmission unit can transmit encoded video / image information or data output in the form of a bitstream to the receiving unit of a receiving device via a digital storage medium or network in the form of a file or streaming. The digital storage medium can include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. The transmission unit can include an element for generating a media file via a predetermined file format and can include an element for transmission via a broadcasting / communication network. The receiving unit can extract the bitstream and transmit it to a decoding device.

[0066] The receiver can receive mesh video data transmitted by a mesh video transmission device. Depending on the transmission channel, the receiver can receive mesh video data via a broadcast network, via broadband, or via digital storage media.

[0067] The receiving processing unit can perform processing on the received mesh video data according to a transmission protocol. The receiving processing unit can be included in the receiving unit, or can be configured as a separate component / module. In response to the processing performed for transmission on the transmitting side, the receiving processing unit can perform the reverse process of the aforementioned transmitting processing unit. The receiving processing unit can transfer the acquired mesh video data to the decapsulation processing unit, and transfer the acquired mesh video-related metadata to a metadata parser. The mesh video-related metadata acquired by the receiving processing unit can be in the form of a signaling table.

[0068] A decapsulation processing unit (file / segment decapsulation module) can decapsulate mesh video data in file format received from a receiving processing unit. The decapsulation processing unit can decapsulate files according to ISOBMFF, etc., to obtain a mesh video bitstream or mesh video-related metadata (metadata bitstream). The obtained mesh video bitstream can be transmitted to a mesh video decoder, and the obtained mesh video-related metadata (metadata bitstream) can be transmitted to a metadata processing unit. The mesh video bitstream may include metadata (metadata bitstream). The metadata processing unit may be included in the mesh video decoder, or may be configured as a separate component / module. The mesh video-related metadata obtained by the decapsulation processing unit may be in the form of a box or track within a file format. If necessary, the decapsulation processing unit may receive metadata required for decapsulation from the metadata processing unit. Mesh video related metadata can be passed to a Mesh video decoder for use in the Mesh video decoding process, or passed to a renderer for use in the Mesh video rendering process.

[0069] A mesh video decoder can receive a bitstream and perform operations corresponding to those of a mesh video encoder to decode video / images. The decoded mesh video can be displayed via a display unit. Users can view all or part of the rendered result via a VR / AR display or a general display.

[0070] The feedback process may include a process of transmitting various feedback information that may be acquired during the rendering / display process to the transmitter or to the decoder on the receiver. Interactivity may be provided in mesh video consumption through the feedback process. Depending on the embodiment, head orientation information, viewport information indicating the area that the user is currently viewing, etc. may be transmitted during the feedback process. Depending on the embodiment, the user may interact with things implemented in the VR / AR / MR / autonomous driving environment, in which case information related to the interaction may be transmitted to the transmitter or the service provider during the feedback process. Depending on the embodiment, the feedback process may not be performed.

[0071] Head orientation information can refer to information about the user's head position, angle, and movement. Based on this information, information about the area the user is currently viewing within the mesh video, i.e. viewport information, can be calculated.

[0072] Viewport information can be information about the area the user is currently viewing in the mesh video. This can be used to perform gaze analysis to determine how the user consumes the mesh video, which area of ​​the mesh video they are gazing at, and for how long. Gaze analysis can be performed on the receiving side and transmitted to the transmitting side through a feedback channel. Devices such as VR / AR / MR displays can extract the viewport area based on the user's head position / orientation, the vertical or horizontal FOV supported by the device, etc.

[0073] Depending on the embodiment, the aforementioned feedback information may not only be transmitted to the transmitter but may also be consumed by the receiver. That is, the aforementioned feedback information may be utilized to perform decoding, rendering, and other processes on the receiver. For example, head orientation information and / or viewport information may be utilized to preferentially decode and render only the mesh video for the area currently being viewed by the user.

[0074] This document relates to dynamic mesh video compression as described above. The method / embodiment disclosed in this document can be applied to the Video-based Dynamic Mesh Compression (V-Mesh) standard of the Moving Picture Experts Group (MPEG) or the next-generation video / image coding standard. Dynamic mesh video compression is a method for processing mesh connection information and properties that change over time, and it can perform lossy and lossless compression for various applications such as real-time communication, storage, free-view video, and AR / VR.

[0075] The dynamic mesh video compression method described below is based on MPEG's V-Mesh method.

[0076] In this document, picture / frame can generally mean a unit representing one video of a specific time period.

[0077] A pixel or pel can refer to the smallest unit that constitutes a picture (or image). Additionally, the term "sample" can be used as a counterpart to a pixel. A sample can generally represent a pixel or a pixel value, and can represent only the pixel / pixel value of the luma component, only the pixel / pixel value of the chroma component, or only the pixel / pixel value of the depth component.

[0078] A unit may represent a basic unit of image processing. A unit may include at least one of a specific region of a picture and information related to the region. In some cases, the term "unit" may be used interchangeably with terms such as "block" or "area." In general, an MxN block may include a set (or array) of samples (or sample array) or transform coefficients consisting of M columns and N rows.

[0079] The encoding process of Fig. 1 is as follows.

[0080] Video-based dynamic mesh compression (V-Mesh) compression methods can provide a method for compressing dynamic mesh video data based on 2D video codecs such as HEVC and VVC. The V-Mesh compression process receives the following data as input and performs compression.

[0081] Input mesh: Contains the 3D coordinates (geometry) of the vertices that make up the mesh, normal information for each vertex, mapping information that maps the mesh surface to a 2D plane, and connection information between the vertices that make up the surface. The mesh surface can be expressed as triangles or more polygons, and connection information between the vertices that make up each surface is stored according to a set shape. The input mesh can be saved in the OBJ file format.

[0082] Attribute map: (Hereinafter, texture map is also used in the same meaning): Contains information about the properties (color, normal, displacement, etc.) of the mesh, and stores data in the form of a mapping of the surface of the mesh onto a 2D image. Mapping which part (surface or vertex) of the mesh each data of this attribute map corresponds to is based on the mapping information contained in the input mesh. Since the attribute map has data for each frame of the mesh video, it can also be expressed as an attribute map video (or attribute for short). The attribute map in the V-Mesh compression method mainly contains the color information of the mesh, and is saved in an image file format (PNG, BMP, etc.).

[0083] Material Library File: Contains information about the material properties used in a mesh, particularly information that links the input mesh to its corresponding attribute map. It is saved in the Wavefront Material Template Library (MTL) file format.

[0084] In the V-Mesh compression method, the following data and information can be generated through the compression process.

[0085] Base mesh: The input mesh is simplified (decimated) through a preprocessing process to express the objects of the input mesh using the minimum number of vertices determined by the user's standards.

[0086] Displacement: This is displacement information used to express the input mesh as similarly as possible to the base mesh, and is expressed in the form of 3D coordinates.

[0087] Atlas information: This is the metadata required to reconstruct a mesh using base mesh, displacement, and attribute map information. It can be created and utilized as sub-mesh units (such as patches) that make up the mesh.

[0088] Referring to FIGS. 2 to 7, a method for encoding mesh position information (vertex) is described, and referring to FIGS. 6-10, etc., a method for encoding attribute information (attribute map) by restoring mesh position information is described.

[0089] Figure 2 illustrates a V-MESH compression method according to embodiments.

[0090] Fig. 2 illustrates the encoding process of Fig. 1, and the encoding process may include a pre-processing process and an encoding process. The encoder of Fig. 1 may include a pre-processor (200) and an encoder (201) as in Fig. 2. The transmitting device of Fig. 1 may be broadly referred to as an encoder, and the dynamic mesh video encoder of Fig. 1 may be referred to as an encoder. The V-Mesh compression method may include a pre-processing (200) and an encoding (201) process as in Fig. 2. The pre-processor of Fig. 2 may be located in front of the encoder of Fig. 2. The pre-processor and the encoder of Fig. 2 may be referred to as a single encoder.

[0091] The preprocessor can receive a static dynamic mesh and / or an attribute map. The preprocessor can generate a base mesh and / or displacement through preprocessing. The preprocessor can receive feedback information from the encoder and generate the base mesh and / or displacement based on the feedback information.

[0092] The encoder can receive a base mesh, displacement mesh, static dynamic mesh, and / or attribute map. The encoder can encode mesh-related data to generate a compressed bitstream.

[0093] Figure 3 illustrates pre-processing of V-MESH compression according to embodiments.

[0094] Figure 3 shows the configuration and operation of the pre-processor of Figure 2.

[0095] Fig. 3 shows a process of performing preprocessing on an input mesh. The preprocessing process (200) can be broadly divided into four steps: 1) Group of Frame (GoF) generation, 2) Mesh Decimation, 3) UV parameterization, and 4) Fitting subdivision surface (300). The preprocessor (200) can receive an input mesh, generate a displacement and / or base mesh, and transmit the generated displacement and / or base mesh to the encoder (201). The preprocessor (200) can transmit GoF information related to GoF generation to the encoder (201).

[0096] Below, each step of Figure 3 is described.

[0097] GoF Generation: This is the process of generating a reference structure for mesh data. If the number of vertices, number of texture coordinates, vertex connection information, and texture coordinate connection information of the mesh of the previous frame and the current mesh are all the same, the previous frame can be set as the reference frame. In other words, if only the vertex coordinate values ​​are different between the current input mesh and the reference input mesh, inter-frame encoding can be performed. Otherwise, the frame performs intra-frame encoding.

[0098] Mesh Decimation: This process simplifies the input mesh to create a simplified mesh, or base mesh. Vertices to be removed from the original mesh are selected based on user-defined criteria, and the selected vertices and the triangles connected to them can be removed.

[0099] In the process of performing mesh simplification (Mesh decimation), the input mesh (voxelized), target triangle ratio (TTR), and minimum triangle component (CCCount) information are passed as input, and the simplified mesh (decimated mesh) can be obtained as output. In this process, connected triangle components smaller than the set minimum triangle component (CCCount) can be removed.

[0100] UV parameterization: This is the process of mapping a 3D surface of a decimated mesh into a texture domain. Parameterization can be performed using the UVAtlas tool. This process generates mapping information, which indicates where each vertex of the decimated mesh can be mapped to on a 2D image. This mapping information is expressed and stored as texture coordinates, and through this process, the final base mesh is created.

[0101] Fitting subdivision surface: This is the process of performing subdivision on a simplified mesh. The subdivision method can be a user-defined method, such as the mid-edge method. The fitting process ensures that the input mesh and the subdivision mesh are similar to each other.

[0102] Figure 4 illustrates a mid-edge subdivision method according to embodiments.

[0103] Figure 4 illustrates the mid-edge method of the fitting subdivision surface described in Figure 3. Referring to Figure 4, an original mesh containing four vertices is subdivided to create a sub-mesh. A sub-mesh can be created by creating a new vertex midway between the edges between the vertices.

[0104] When a fitted subdivided mesh (hereinafter referred to as a fitted subdivided mesh) is generated, displacement is calculated using this result and a pre-compressed and decrypted base mesh (hereinafter referred to as a reconstructed base mesh). That is, the reconstructed base mesh is subdivided in the same way as the fitting subdivision surface. The difference in position of each vertex between this result and the fitted subdivided mesh is the displacement for each vertex. Since displacement represents a position difference in three-dimensional space, it is also expressed as a value in the (x, y, z) space of a Cartesian coordinate system. Depending on the user input parameters, the (x, y, z) coordinate values ​​can be converted to (normal, tangential, bi-tangential) coordinate values ​​of the local coordinate system.

[0105] Figure 5 shows a displacement generation process according to embodiments.

[0106] FIG. 5 illustrates in detail the displacement calculation method of the fitting subdivision surface (300) as described in FIG. 4.

[0107] An encoder and / or pre-processor according to embodiments may include 1) a subdivision unit, 2) a local coordinate system calculation unit, and 3) a displacement calculation unit. The subdivision unit may receive a reconstructed base mesh and generate a subdivided reconstructed base mesh. The local coordinate system calculation unit may receive a fitted subdivision mesh and a subdivided reconstructed base mesh, and transform a coordinate system of the mesh into a local coordinate system. The local coordinate system calculation operation may be optional. The displacement calculation unit may calculate a positional difference between the fitted subdivision mesh and the subdivided reconstructed base mesh. For example, a positional difference value between vertices of two input meshes may be generated. The vertex positional difference value becomes a displacement.

[0108] The method and device for transmitting point cloud data according to the embodiments can encode the point cloud as follows. The point cloud data (which may be referred to as a point cloud for short) according to the embodiments can refer to data including vertex coordinates and color information. The term "point cloud" includes mesh data, and in this document, point cloud and mesh data can be used interchangeably.

[0109] The V-Mesh compression (reconstruction) method according to the embodiments may include intra frame encoding (Fig. 6) and inter frame encoding (Fig. 7).

[0110] Based on the results of the GoF generation described above, intra-frame encoding or inter-frame encoding is performed. In the case of intra-encoding, the data to be compressed may be a base mesh, displacement, attribute map, etc. In the case of inter-encoding, the data to be compressed may be a displacement, attribute map, and a motion field between a reference base mesh and the current base mesh.

[0111] FIG. 6 illustrates an intra-frame encoding process of a V-MESH compression method according to embodiments.

[0112] The encoding process of Fig. 6 details the encoding of Fig. 1. That is, it shows the configuration of an encoder when the encoding of Fig. 1 is an intra-frame method. The encoder of Fig. 6 may include a preprocessor (200) and / or an encoder (201).

[0113] The preprocessor can receive an input mesh and perform the preprocessing described above. The preprocessing can generate a base mesh and / or a fitted subdivided mesh. The quantizer can quantize the base mesh and / or the fitted subdivided mesh. The static mesh encoder can encode the static mesh. The static mesh encoder can generate a bitstream including the encoded base mesh. The static mesh decoder can decode the encoded static mesh. The inverse quantizer can inversely quantize the quantized static mesh. The displacement calculation unit can receive the reconstructed static mesh and generate displacement, which is a position difference, based on the fitted subdivided mesh. The forward linear lifting unit can receive the displacement and generate lifting coefficients. The quantizer can quantize the lifting coefficients. The image packing unit can pack an image based on the quantized lifting coefficients. A video encoder can encode a packed image. A video decoder decodes the encoded video. An image unpacker can unpack a packed image. A dequantizer can inversely quantize an image. An inverse linear lifting unit applies inverse lifting to the image to generate a reconstructed displacement. A mesh restoration unit restores a warped mesh using the reconstructed displacement and the reconstructed base mesh. An attribute transfer unit receives an input mesh and / or an input attribute map, and generates an attribute map based on the reconstructed warped mesh. A push-pull padding unit can pad data in the attribute map based on a push-pull method. A color space transformation unit can transform the space of a color component, which is an attribute. A video encoder can encode an attribute. A multiplexer can generate a bitstream by multiplexing a compressed base mesh, compressed displacement, and compressed attributes.

[0114] Figure 7 illustrates an inter-frame encoding process of a V-MESH compression method according to embodiments.

[0115] The encoding process of Fig. 7 details the encoding of Fig. 1. That is, it shows the configuration of an encoder when the encoding of Fig. 1 is an inter-frame method. The encoder of Fig. 7 may include a preprocessor (200) and / or an encoder (201).

[0116] Among the encoding operations of Fig. 7, the corresponding configuration of the encoding operation of Fig. 6 refers to the description of Fig. 7. For the inter-frame-based encoding of Fig. 7, the motion encoder can encode motion based on the restored quantized reference base mesh. The base mesh restoration unit can restore the base mesh based on the restored quantized reference base mesh.

[0117] The encoder of Fig. 6 generates a bitstream by compressing the base mesh, displacement, and attributes within the frame, and the encoder of Fig. 7 generates a bitstream by compressing the motion, displacement, and attributes between the current frame and the reference frame.

[0118] The encoding method according to the embodiments includes base mesh encoding (intra encoding). When performing intra frame encoding on the current input mesh frame, the base mesh generated in the preprocessing process can be encoded using a static mesh compression technique after going through a quantization process. In the V-Mesh compression method, for example, Draco technology is applied, and the vertex position information, mapping information (texture coordinates), vertex connection information, etc. of the base mesh are compressed.

[0119] The encoding method according to the embodiments may include motion field encoding (inter encoding). Inter frame encoding may be performed when a one-to-one correspondence of vertices is established between a reference mesh and a current input mesh, and only the position information of the vertices is different. When performing inter frame encoding, instead of compressing the base mesh, the difference between the vertices of the reference base mesh and the current base mesh, i.e., the motion field, may be calculated and this information may be encoded. The reference base mesh is the result of quantizing the already decoded base mesh data and is determined according to the reference frame index determined in the GoF generation. The motion field may be encoded as a value. Alternatively, the predicted motion field may be calculated by averaging the motion fields of the restored vertices among the vertices connected to the current vertex, and this predicted motion field The residual motion field, which is the difference between the value and the motion field value of the current vertex, can be encoded. This value can be encoded using entropy coding. The process of encoding the displacement and attribute map, excluding the motion field encoding process of inter-frame encoding, is the same as the structure of the intra-frame encoding method except for the base mesh encoding.

[0120] Figure 8 shows a lifting conversion process for displacement according to embodiments.

[0121] Figure 9 illustrates a process of packing transformation coefficients according to embodiments into a 2D image.

[0122] Figures 8-9 show the process of converting the displacement of the encoding process of Figures 6-7 and the process of packing the conversion coefficients, respectively.

[0123] The encoding method according to the embodiments includes displacement encoding.

[0124] After encoding the base mesh through base mesh encoding and / or motion field encoding, a reconstructed base mesh is generated through restoration and dequantization, and the displacement between the result of performing subdivision on the reconstructed base mesh and the fitted subdivided mesh generated through the fitting subdivision surface can be calculated. For effective encoding, a data transform process such as wavelet transform can be applied to the displacement information.

[0125] Figure 8 shows the process of transforming displacement information using lifting transform in V-Mesh. The transform coefficients generated through the transform process are quantized and then packed into a 2D image as shown in Figure 9. The transform coefficients are organized into one block for each 256 (=16×16) units, and each block can be packed in z-scan order. The horizontal number of blocks is fixed to 16, but the vertical number of blocks can be determined according to the number of vertices of the subdivided base mesh. The transform coefficients can be packed by sorting them with Morton code within a block. The packed images generate a displacement video for each GoF unit, and this displacement video can be encoded using an existing video compression codec.

[0126] Referring to FIG. 8, the base mesh (original) may include vertices and edges for LoD0. The first subdivision mesh generated by dividing the base mesh includes vertices generated by further dividing the edges of the base mesh. The first subdivision mesh includes vertices for LoD0 and vertices for LoD1. LoD1 includes the subdivided vertices and the vertices (LoD0) of the base mesh. The first subdivision mesh may be generated by dividing the second subdivision mesh. The second subdivision mesh includes LoD2. LoD2 includes the base mesh vertices (LoD0), LoD1 including the vertices additionally generated from LoD0, and the vertices additionally divided from LoD1. LoD is a level indicating the degree of detail (Level of Detail), and as the level index increases, the distance between vertices becomes closer and the level of detail increases. LoD N includes the vertices included in the previous LoDN-1 as they are. When a vertex is further divided through subdivision, considering the previous vertices v1, v2 and the subdivided vertex v, the mesh can be encoded based on a prediction and / or update method. Instead of still encoding information about the current LoD N, a residual value between the previous LoD N-1 can be generated, and the mesh can be encoded using the residual value to reduce the size of the bitstream. The prediction process means the operation of predicting the current vertex v using the previous vertices v1, v2. Since adjacent subdivision meshes have similar data, efficient encoding can be achieved by utilizing this property. The current vertex position information is predicted as the residual for the previous vertex position information, and the previous vertex position information is updated using the residual.

[0127] Referring to Figure 9, the vertices have coefficients generated through the lifting transformation. The coefficients of the vertices related to the lifting transformation can be encoded by packing them into an image.

[0128] Fig. 10 shows an attribute transfer process of a V-MESH compression method according to embodiments.

[0129] Figure 10 shows the detailed operation of attribute transfer of encoding such as Figures 6-7.

[0130] Encoding according to embodiments includes attribute map encoding.

[0131] Information about the input mesh is compressed through base mesh encoding, motion field encoding, and displacement encoding. In the encoding process, the compressed input mesh is restored through base mesh decoding (intra frame), motion field decoding (inter frame), and displacement video decoding, and the restored result, the reconstructed deformed mesh (hereinafter referred to as Recon. deformed mesh), is used to compress the input attribute map as shown in FIGS. 6 and 7. The reconstructed deformed mesh (Recon. deformed mesh) has vertex position information, texture coordinates, and corresponding connection information, but does not have color information corresponding to the texture coordinates. Therefore, as shown in Fig. 10, in the V-Mesh compression method, a new attribute map having color information corresponding to the texture coordinates of the reconstructed deformed mesh is created through the attribute transfer process.

[0132] Attribute transfer first checks whether each point P(u, v) in the 2D texture domain belongs to a texture triangle of the reconstructed deformed mesh, and if it is in the texture triangle T, calculates the barycentric coordinate (α, β γ) of P(u, v) according to the triangle T. Then, using the 3D vertex position and (α, β γ) of triangle T, calculate the 3D coordinate M(x, y, z) of P(u, v). Find the vertex coordinate M'(x', y', z') that corresponds to the position most similar to the calculated M(x, y, z) in the input mesh domain and the triangle T' that contains this point. And in this triangle T', the center of mass coordinates (α', β', γ') of M'(x', y', z') are calculated. Using the texture coordinates corresponding to the three vertices of triangle T' and (α', β', γ'), the texture coordinates (u', v') are calculated, and the color information corresponding to these coordinates is found in the input attribute map. The color information found in this way is immediately assigned to the pixel location (u, v) of the new attribute map. If P(u, v) does not belong to any triangle, the pixel at that location in the new attribute map can be filled with a color value using a padding algorithm such as the push-pull algorithm.

[0133] The new attribute map generated through attribute transfer is grouped into GoF units to form an attribute map video, which is then compressed using a video codec.

[0134] Referring to Figure 10, the reference relationship between the input mesh, input attribute map, restored mesh, and generated attribute map can be seen.

[0135] The decoding process of Fig. 1 can perform the reverse process of the corresponding encoding process of Fig. 1. The specific decoding process is as follows.

[0136] Fig. 11 illustrates an intra-frame decoding process of a V-MESH compression method according to embodiments.

[0137] Fig. 11 shows the configuration and operation of a decoder of a receiving device such as Fig. 1.

[0138] Figure 11 illustrates the intra decoding process of V-Mesh technology. First, the input bitstream can be separated into a mesh sub-stream, a displacement sub-stream, an attribute map sub-stream, and a sub-stream containing mesh patch information, such as V3C / V-PCC.

[0139] The mesh sub-stream is decoded by the decoder of the static mesh codec used in encoding, such as Google Draco, and as a result, the connection information, vertex geometry information, vertex texture coordinates, etc. of the base mesh can be restored. The displacement sub-stream is decoded into a displacement video by the decoder of the video compression codec used in encoding, and goes through the image unpacking, inverse quantization, and inverse transform processes to restore displacement information for each vertex. Inverse quantization is applied to the restored base mesh, and this result is combined with the restored displacement information to generate the final decoded mesh.

[0140] The attribute map sub-stream is decoded through the decoder of the video compression codec used in encoding, and then restored to the final attribute map through processes such as color format conversion.

[0141] The restored decoded mesh and decoded attribute map can be utilized by the receiver as final mesh data that can be utilized by the user.

[0142] Referring to FIG. 11, the bitstream includes patch information, a mesh substream, a displacement substream, and an attribute map substream. The term "substream" is interpreted as referring to a portion of the bitstream included in the bitstream. The bitstream includes patch information (data), mesh information (data), displacement information (data), and attribute map information (data).

[0143] The decoder performs the following decoding operations within the frame. The static mesh decoder decodes the mesh to generate a reconstructed quantized base mesh, and the inverse quantizer applies the quantization parameters of the quantizer inversely to generate the reconstructed base mesh. The video decoder decodes the displacement, the unpacker unpacks the decoded video image, and the inverse quantizer inversely quantizes the quantized image. The linear lifting inverse transform applies a lifting transform in the reverse process of the encoder to generate the reconstructed displacement. The mesh restoration unit generates a warped mesh based on the base mesh and the displacement. The video decoder decodes the attribute map, and the color transformation unit transforms the color format and / or space to generate the decoded attribute map.

[0144]

[0145] Figure 12 shows the inter-frame decoding process of the V-MESH compression method.

[0146] Fig. 12 shows the configuration and operation of the decoder of the receiving device of Fig. 1.

[0147] Figure 12 illustrates the inter-decoding process of V-Mesh technology. First, the input bitstream can be separated into a motion sub-stream, a displacement sub-stream, an attribute sub-stream, and a sub-stream containing mesh patch information, such as V3C / V-PCC.

[0148] The motion sub-stream is decoded through entropy decoding and inverse prediction processes, and the reconstructed motion information is combined with the already reconstructed reference base mesh to generate a reconstructed quantized base mesh for the current frame. The result of applying inverse quantization to this is combined with the displacement information reconstructed in the same way as the intra decoding described above to generate the final decoded mesh. The attribute map sub-stream is decoded in the same way as the intra decoding. The reconstructed decoded mesh and the decoded attribute map can be utilized by the receiver as the final mesh data that can be utilized by the user.

[0149] Referring to Fig. 12, the bitstream includes motion, displacement, and attribute maps. Since inter-frame decoding is performed, a process of decoding inter-frame motion information is further included. The motion is decoded, and a restored quantized base mesh for the motion is generated based on the reference base mesh, thereby generating a restored base mesh. For a description of the operations in Fig. 12, which are identical to those in Fig. 11, refer to the description in Fig. 11.

[0150] Fig. 13 shows a point cloud data transmission device according to embodiments.

[0151] Fig. 13 corresponds to the transmitting device (100), the dynamic mesh video encoder (102), the encoder (preprocessor and encoder) of Fig. 2, and / or the transmitting encoding device corresponding thereto of Fig. 13. Each component of Fig. 13 corresponds to hardware, software, a processor, and / or a combination thereof.

[0152] The operation process of a transmitter for compressing and transmitting dynamic mesh data using V-Mesh compression technology may be as shown in Fig. 13.

[0153] The mesh preprocessor receives the original mesh as input and generates a simplified mesh (decimated mesh). Simplification can be performed based on the target number of vertices or the target number of polygons that constitute the mesh. Parameterization can be performed on the simplified mesh to generate texture coordinates and texture connection information per vertex. Additionally, quantization of floating-point mesh information into fixed-point information can be performed. This result can be encoded as a base mesh through a static mesh encoding unit. The mesh preprocessor can perform mesh subdivision on the base mesh to generate additional vertices. Depending on the subdivision method, vertex connection information, texture coordinates, and texture coordinate connection information including the added vertices can be generated. The subdivided mesh can be fitted by adjusting the vertex positions to resemble the original mesh, thereby generating a fitted subdivided mesh.

[0154] When performing intra-encoding on the corresponding mesh frame, the base mesh generated through the mesh preprocessing unit can be compressed through the static mesh encoding unit. In this case, encoding can be performed on the connection information, vertex geometry information, vertex texture information, normal information, etc. of the base mesh. The base mesh bitstream generated through encoding is transmitted to the multiplexing unit.

[0155] When performing inter encoding for the corresponding mesh frame, a motion vector encoding unit is performed, which can calculate a motion vector between the base mesh and the reference reconstruction base mesh as input and encode the value. The motion vector encoding unit can perform prediction based on connection information using a previously encoded / decoded motion vector as a predictor, and encode a residual motion vector obtained by subtracting the predicted motion vector from the current motion vector. The motion vector bitstream generated through encoding is transmitted to the multiplexing unit.

[0156] The encoded base mesh and motion vectors can be used to generate a restored base mesh through the base mesh restoration unit.

[0157] The displacement vector calculator can perform mesh refinement on the restored base mesh. The displacement vector can be calculated as the difference in vertex positions between the refined restored base mesh and the fitted subdivision mesh generated in the preprocessing unit. As a result, the number of displacement vectors can be calculated equal to the number of vertices in the refined mesh. The displacement vector calculation unit can convert the displacement vector calculated in the 3D Cartesian coordinate system into a local coordinate system based on the normal vector of each vertex.

[0158] A displacement vector video generator can transform displacement vectors for effective encoding. The transformation can be performed by a lifting transformation, a wavelet transformation, etc., depending on the embodiment. In addition, quantization can be performed on the transformed displacement vector values, i.e., the transform coefficients. Different quantization parameters can be applied to each axis of the transform coefficients, and the quantization parameters can be derived according to the promise of the encoder / decoder. The transformed and quantized displacement vector information can be packed into a 2D image. A displacement vector video can be generated by bundling the packed 2D images for each frame, and the displacement vector video can be generated for each GoF (Group of Frame) unit of the input mesh.

[0159] A displacement vector video encoder can encode the generated displacement vector video using a video compression codec. The generated displacement vector video bitstream is transmitted to a multiplexer.

[0160] The displacement vector restored through the displacement vector restorer and the base mesh restored through the base mesh restorer and refined are restored through the mesh restorer, and the restored mesh has restored vertices, connection information between vertices, texture coordinates, and connection information between texture coordinates.

[0161] The texture map of the original mesh can be regenerated as a texture map for the restored mesh through the texture map video generation unit. The color information per vertex of the texture map of the original mesh can be assigned to the texture coordinates of the restored mesh. The regenerated texture maps for each frame can be bundled into GoF units to generate a texture map video.

[0162] The generated texture map video can be encoded using a video compression codec through a texture map video encoding unit. The texture map video bitstream generated through encoding is transmitted to a multiplexing unit.

[0163] The generated motion vector bitstream, base mesh bitstream, displacement vector bitstream, and texture map bitstream may be multiplexed into a single bitstream and transmitted to a receiver via a transmitter. Alternatively, the generated motion vector bitstream, base mesh bitstream, displacement vector bitstream, and texture map bitstream may be generated as a file with one or more track data or encapsulated into segments and transmitted to a receiver via a transmitter.

[0164] Referring to FIG. 13, a transmitting device (encoder) can encode a mesh in an intra-frame or inter-frame manner. A transmitting device according to intra-encoding can generate a base mesh, a displacement vector (displacement), and a texture map (attribute map). A transmitting device according to inter-encoding can generate a motion vector (motion), a base mesh, a displacement vector (displacement), and a texture map (attribute map). A texture map obtained from a data input unit is generated and encoded based on a restored mesh. Displacement is generated and encoded through the difference in vertex positions between the base mesh and the segmented mesh. The base mesh is generated by preprocessing, simplifying, and encoding the original mesh. Motion is generated as a motion vector for the mesh of the current frame based on the reference base mesh of the previous frame.

[0165] Fig. 14 shows a point cloud data receiving device according to embodiments.

[0166] Fig. 14 corresponds to the receiving device (110), the dynamic mesh video decoder (113), the decoder of Figs. 11-12, and / or the receiving decoding device corresponding thereto of Fig. 1. Each component of Fig. 14 corresponds to hardware, software, a processor, and / or a combination thereof. The receiving (decoding) operation of Fig. 14 may follow the reverse process of the corresponding process of the transmitting (encoding) operation of Fig. 13.

[0167] The bitstream of the received Mesh is demultiplexed into a compressed motion vector bitstream or base mesh bitstream, displacement vector bitstream, and texture map bitstream after file / segment decapsulation.

[0168] If the current mesh has inter-frame encoding applied according to the frame header information, the motion vector decoding unit can perform decoding on the motion vector bitstream. The final motion vector can be reconstructed by adding the previously decoded motion vector to the residual motion vector decoded from the bitstream using the previously decoded motion vector as a predictor.

[0169] If the current mesh has been encoded within the screen according to the frame header information, the base mesh bitstream can restore the connection information, vertex geometry information, texture coordinates, normal information, etc. of the base mesh through the static mesh encoding unit.

[0170] In the base mesh restoration unit, if the current mesh has inter-frame encoding applied, the current base mesh can be restored by adding the decoded motion vector to the reference base mesh and then performing inverse quantization. If the current mesh has intra-frame encoding applied, the static mesh decoding unit can perform inverse quantization on the decoded mesh to generate a restored base mesh.

[0171] The displacement vector bitstream can be decoded as a video bitstream using a video codec in a displacement vector video decoding unit.

[0172] In the displacement vector restoration unit, displacement vector transformation coefficients are extracted from the decoded displacement vector video, and the displacement vector is restored through the inverse quantization and inverse transformation processes. If the restored displacement vector is a value in the local coordinate system, a process of inverse transformation to the Cartesian coordinate system can be performed.

[0173] The mesh restoration unit can generate additional vertices by performing subdivision on the restored base mesh. Subdivision can generate vertex connection information, texture coordinates, and texture coordinate connection information, including the added vertices. The subdivided restored base mesh can be combined with the restored displacement vector to generate the final restored mesh.

[0174] The texture map bitstream can be decoded as a video bitstream using a video codec in a texture map video decoding unit. The restored texture map contains color information for each vertex contained in the restored mesh, and the color value of each vertex can be obtained from the texture map using the texture coordinates of the corresponding vertex.

[0175] The restored mesh and texture map are displayed to the user through a rendering process using a mesh data renderer, etc.

[0176] Referring to FIG. 14, a receiving device (decoder) can decode a mesh in an intra-frame or inter-frame manner. A receiving device according to intra-decoding can receive a base mesh, a displacement vector (displacement), and a texture map (attribute map), and decode the restored mesh and the restored texture map to render the mesh data. A receiving device according to inter-decoding can receive a motion vector (motion), a base mesh, a displacement vector (displacement), and a texture map (attribute map), and decode the restored mesh and the restored texture map to render the mesh data.

[0177] A point cloud data encoding device and method according to embodiments can encode mesh data and transmit a bitstream including the encoded mesh data. A point cloud data decoding device and method according to embodiments can receive a bitstream including mesh data and decode the mesh data. The point cloud data encoding / decoding method / device according to embodiments may be referred to as the method / device according to embodiments. The point cloud data encoding / decoding method / device according to embodiments may also be referred to as the mesh data encoding / decoding method / device according to embodiments. In addition, the term encoding / decoding method / device may be used in this document for short.

[0178] The encoding method / device according to the embodiments includes and can perform the following: a transmitting device (100) of FIG. 1, a mesh encoder (102), a file / segment encapsulator (103), a transmitter (104), a pre-processor of FIG. 2, FIG. 3, FIG. 4, FIG. 6, and FIG. 7, an encoder, a bitstream generation of FIG. 13, an encoder of FIG. 15, a syntax generation of FIG. 17 to FIG. 24, a syntax generation of FIG. 29 to FIG. 31, an encoding method of FIG. 33, etc.

[0179] The decryption method / device according to the embodiments may include and perform a receiving device (110) of FIG. 1, a receiving unit (111), a file / segment decapsulator (112), a mesh decoder (113), a renderer (114), a decoder of FIG. 11 and FIG. 12, a decoder of FIG. 14, a bitstream parsing of FIG. 15, a decoder of FIG. 25 to FIG. 28, a syntax parsing of FIG. 29 to FIG. 31, a decryption method of FIG. 34, etc.

[0180] Methods and devices according to embodiments include a partial displacement decoding method for dynamic mesh data.

[0181] Methods and devices according to embodiments include a LoD-based displacement decoding method for dynamic mesh data.

[0182] The embodiments relate to V-DMC (Video-based Dynamic Mesh Compression), a method for compressing 3D dynamic mesh data using an existing 2D video codec. When a displacement vector is compressed through a video codec in a displacement vector encoding / decoding process, a V-DMC decoder / decoder performs a process of packing quantized displacement vector transform coefficients into one frame for each LoD level. The embodiments include a method for partially extracting and decoding a displacement vector bitstream of a specific LoD level in order to decode the mesh up to a specific LoD level desired by the decoder when the displacement vector of the dynamic mesh is encoded through a video codec. By extracting and decoding a displacement vector bitstream up to a specific LoD level according to a receiver state, a network environment, etc., geometric information scalability of dynamic mesh compression can be supported.

[0183] The decoder further includes a method for extracting a portion of the displacement vector bitstream at a specific LoD level to decode the mesh up to a specific LoD level. Depending on the receiver status, network environment, etc., the displacement vector bitstream can be extracted and decoded up to a specific LoD level, thereby decoding a specific LoD mesh.

[0184] The embodiments relate to V-DMC, a method for compressing 3D dynamic mesh data using an existing 2D video codec, and include a method for supporting partial extraction and independent decoding from a displacement vector video bitstream of a dynamic mesh up to a specific LoD level, and a method for generating / parsing syntax and semantics information, which are signaling information related thereto.

[0185] Additionally, the method according to the embodiments further includes a method for supporting extraction and decoding of a sub-bitstream from a displacement vector video bitstream of a dynamic mesh up to a specific LoD level and a method for generating / parsing syntax and semantics information related thereto.

[0186] Recently, V-DMC technology has been actively standardized since the CfP Response in April 2022. The current V-DMC standard technology includes a method of packing quantized displacement vector transform coefficients into a single frame by LoD level in the case of a dynamic mesh encoder / decoder, and when the displacement vector encoder / decoder is a video codec. Embodiments include a method of partially extracting and decoding displacement vector transform coefficients up to a specific LoD level from a displacement vector bitstream level. Embodiments can support geometric information scalability of dynamic meshes by partially extracting and decoding displacement vectors, which are one of the geometric information of the mesh, by LoD level.

[0187] Embodiments can support geometric information scalability of a dynamic mesh through a method for extracting a bitstream corresponding to a specific LoD level from a displacement vector bitstream level when the displacement vector is compressed through a video codec during the displacement vector encoding / decoding process of the dynamic mesh.

[0188] Figure 15 shows a bitstream according to embodiments.

[0189] The encoding method / device according to the embodiments can encode mesh data and generate parameter information (which can be referred to as signaling information, syntax elements, etc.) regarding the mesh data, thereby generating a bitstream as in Fig. 15. The decoding method / device according to the embodiments can receive a bitstream as in Fig. 15 and decode the mesh data based on syntax elements in the bitstream.

[0190] The term V-DMC can also be referred to as V-Mesh, and the two terms are used interchangeably. Dynamic mesh content can be encoded with a bitstream structure as shown in Fig. 15. The bitstream can be generated based on the sample stream data unit used when encoding V3C content in the V3C codec specification (ISO / IEC 23090-5).

[0191] The definitions of abbreviations referring to data included in the bitstream are as follows: VPS: V3C / V-DMC Parameter Set, AD: Atlas Data, BMD: Base Mesh Data, DD: Displacement Data (Displacement data may be encoded with arithmetic coding), GVD: Geometry Video Data (Displacement data may be encoded based on a video codec), AVD: Attribute Video Data (Attribute data may be encoded based on video coding), PVD: Packing Video Data (Packing data may be encoded based on video coding), CAD: Common Atlas Data, OVD: Accuracy Video Data, ADD: Arithmetic Coded Displacement Data.

[0192] Figure 16 shows the payload of the V3C unit according to embodiments.

[0193] The bitstream of Fig. 15 may include a V3C unit as in Fig. 16. The payload of the V3C unit may indicate that the payload includes a parameter set or sub-bitstream regarding the data type indicated by the type of the V3C unit.

[0194] The method / device according to the embodiments includes a method capable of independently decoding each LoD (Level of Detail) by partially extracting displacement data at the bitstream level when the V3C content type is GVD, thereby decoding a multi-resolution mesh.

[0195] Fig. 17 shows an encoder according to embodiments.

[0196] An encoding device according to embodiments may be configured like the encoder of FIG. 17. The encoding device (encoder) may include a memory and / or at least one processor. At least one processor may be configured to perform the operations of each component of FIG. 17.

[0197] Mesh Simplification Unit: The mesh simplification unit receives the original mesh and generates a simplified base mesh. The input mesh can be simplified to a target number of vertices or a target number of faces.

[0198] Mesh parameterization: Performs parameterization to generate texture coordinates (e.g. UV coordinates) and texture connection information per vertex of the input mesh.

[0199] Mesh subdivision unit: The mesh subdivision unit can generate additional vertices by performing subdivision on the base mesh. At this time, depending on the subdivision method, geometric information connection information, texture coordinate connection information, and texture coordinates can be implicitly derived and generated. Mesh subdivision can be performed by user parameters or decoder / decoder agreement, and depending on the embodiment, the vertices of the base mesh , perform subdivision 1 to create a new vertex , …, the vertices generated by performing n-th subdivision When defined as can be defined as follows: = ∪ ∪, … , ∪

[0200] Mesh fitting unit: The mesh fitting unit adjusts vertex positions so that the refined mesh becomes similar to the original mesh. Depending on the embodiment, the mesh simplification unit, the mesh parameterization unit, the mesh refinement unit, and the mesh fitting unit may be omitted, and if the processes are omitted, the original mesh may be applied as an input to the mesh quantization unit. At this time, the coordinate information of the original mesh may be applied as an input to the displacement vector calculation unit, and depending on the embodiment, the displacement vector encoding process (displacement vector calculation unit, displacement vector coordinate system conversion unit, displacement vector encoding unit) may be omitted.

[0201] Mesh quantization unit: The mesh quantization unit can quantize geometric information (e.g., x, y, z) in floating-point form or / and texture coordinates (e.g., u, v) or / and normal information (e.g., nx, ny, nz) into fixed-point form. Depending on the embodiment, quantization for specific components may be omitted.

[0202] Static mesh encoding unit: Encodes the connection information, vertex geometry information, vertex texture coordinates, normal information, etc. of the base mesh.

[0203] Motion vector encoding unit: Motion vector encoding can perform motion vector encoding by calculating motion vectors using reference reconstruction base mesh and current base mesh as input. The motion vector encoding unit can perform prediction based on connection information using previously encoded / decoded motion vectors as predictors, and perform entropy encoding on residual motion vectors obtained by subtracting predicted motion vectors from current motion vectors. Depending on the embodiment, motion vector encoding can be performed on a vertex basis or a subgroup basis.

[0204] Displacement Vector Calculation Unit: The displacement vector calculation unit calculates the displacement vector between the fitted subdivision mesh and the restored current base mesh, which is the mesh on which subdivision was performed. The displacement vector calculation unit can calculate the displacement vector of the number of vertices of the subdivision mesh.

[0205] Displacement vector coordinate system transformation unit: The vertex displacement vector calculated in the (x, y, z) space can be transformed into the (normal, tangential, bi-tangential) coordinate system based on the normal vector of each vertex. Depending on the embodiment, only the normal component of the (normal, tangential, bi-tangential) coordinate system can be encoded, and when the coordinate system transformation is applied according to the sub- / decoder agreement, only the normal component can always be encoded, or the encoder can decide to signal a 1-bit flag (onlyNormFlag). In this case, the normal vector can be calculated for each subdivided vertex based on the geometric information and / or connection information of the surrounding vertices. Whether or not to perform the displacement vector coordinate system transformation can be determined by the sub- / decoder agreement, or a coordinate system transformation determination flag (applyLocalCoord) can be transmitted in units such as sequences, GOF (Group of frame), frames, and sub-mesh to determine whether or not to perform the coordinate system transformation.

[0206] Base mesh restoration unit: The base mesh restoration unit restores the base mesh according to the encoding type (inter-frame encoding or intra-frame encoding) of the current mesh. If inter-frame encoding is performed, the current base mesh can be generated by adding a restoration motion vector to the reference restoration base mesh. If the motion vector is not quantized, the motion vector restoration process is omitted, and the current base mesh can be restored using the motion vector calculated by the motion vector encoding unit. If intra-frame encoding is performed, the current base mesh can be restored by performing inverse quantization on the quantized base mesh through the mesh quantization unit.

[0207] Base mesh dequantization unit: The mesh quantization unit performs dequantization using inputs such as restoration geometric information (x, y, z) of the restoration base mesh or / and texture coordinates (u, v) or / and normal information (nx, ny, nz). Depending on the embodiment, dequantization for specific components may be omitted.

[0208] Displacement Vector Restoration Unit: The bitstream encoded by the 2D video encoder, packed into a 2D image / video, is decoded by the 2D video decoder, and depacked. The quantized transform coefficients for which depacking has been performed are quantized and then deconvoluted to calculate the restored displacement vector.

[0209] Mesh Restoration Unit: Subdivision is performed on the restored base mesh, which has been restored through inverse quantization in the base mesh inverse quantization unit, to generate subdivided vertex position information, texture coordinates, and connection information. The restored displacement vector is added to the subdivided vertex position information to generate restored vertex position information.

[0210] Texture map generation unit: The texture map generation unit generates a texture map of the restoration mesh through the relationship between the texture coordinates and connection information of the restoration mesh and the texture map of the original mesh.

[0211] Texture map encoding unit: The texture map generated through the texture map generation unit is stacked in the frame order of the mesh to form a texture map video, which is then encoded through a 2D video encoder. Depending on the embodiment, if the color space of the texture map is RGB444, encoding may be performed after conversion to a color space such as YUV420 or YUV444.

[0212] Figure 18 shows displacement vector encoding according to embodiments.

[0213] Figure 18 illustrates the displacement vector encoding operation of the Figure 17 encoder. Displacement (or displacement data) refers to a set of 3D vectors added to the vertices of a subdivided mesh close to the input mesh. Displacement may also be referred to as a displacement vector, etc.

[0214] The displacement vector encoding unit can perform displacement vector encoding through a 2D video encoder such as H.264, HEVC, or VVC, or can perform encoding through a zero run length encoder or an arithmetic encoder.

[0215] The displacement vector encoding method can be determined as a specific encoding method by a decoder / sub-coder agreement, or the encoding method determined by the encoder can be signaled based on a flag or index (dispEncType), etc.

[0216] Displacement vector encoding methods may vary, and depending on the embodiment, at least one method among the video codec-based encoding method (see Fig. 18 (a)), the zero run-length encoding method (see Fig. 18 (b)), and the arithmetic encoding method (see Fig. 18 (c)) may be determined through the dispEncType flag or index, such as {video codec-based encoding method, zero run-length encoding method}, {video codec-based encoding method, zero run-length encoding method}, {video codec-based encoding method, arithmetic encoding method}.

[0217] Depending on the embodiment, a displacement vector encoding method can be determined according to a profile defined in a decoder / decoder, and an index (profileToolsetIdx) indicating profile information can be signaled so that the decoder can determine a displacement vector decoding method according to profileToolsetIdx.

[0218] An embodiment of a displacement vector encoding unit according to a displacement vector encoding method is as follows.

[0219] As shown in Fig. 18(a), when the displacement vector encoding method is a video codec-based encoding method, the displacement vector transform coefficient packing unit can pack the quantized displacement vector transform coefficients into one frame for each LoD level through the displacement vector transform coefficient quantization unit. The area packed for each LoD level may be in a raster-scan order or may be in a rectangular shape, depending on the embodiment. The packing method may be determined by deriving it in the same way as the decoder / decoder, and the packing method may be determined in the decoder by signaling.

[0220] When coding video, the packed area by LoD level can be divided into MCTS (motion constraint tile set) areas by LoD level depending on the type of video codec, in the case of HEVC, and in the case of VVC, the area can be divided into subpicture areas by LoD level.

[0221] Terms such as MCTS, subpicture, etc. are merely terms classified according to the type of video codec. Both MCTS and subpicture are interpreted as terms referring to partial areas within a frame, and can be interpreted with the same meaning and interchanged.

[0222] Figures 19 and 20 illustrate examples of designating a quantized displacement vector transform coefficient packing area for each LoD according to embodiments as MCTS.

[0223] According to an embodiment, the region for determining the quantized displacement vector transform coefficients as the MCTS region or the subpicture region for each LoD may be as shown in FIGS. 19 and 20. The encoding and decoding methods according to the embodiments may designate the region for each refinement level as the MCTS when encoding / decoding a video for a frame in which displacement vector transform coefficients are packed in a rectangular region for each refinement level. The refinement level may mean vertices excluding the vertices corresponding to the LoD (N-1) mesh in the LoD N mesh. The refinement level may be referred to as a refinement list. For example, in the case of LoD 0, the vertices may be composed of refinement level 0, in the case of LoD 1, the vertices may be composed of refinement levels 0 and 1, and in the case of LoD 2, the vertices may be composed of refinement levels 0, 1, and 2. The encoding / decoding method according to the embodiments may designate an MCTS area by LoD level as in Fig. 19, and LoD 0 may be designated as MCTS 2, LoD 1 as MCTS 1, and LoD 2 as MCTS 0. As in Fig. 20, the MCTS area may be designated by refinement level, and refinement level 0 may be designated as MCTS 2, refinement level 1 as MCTS 1, and refinement level 2 as MCTS 0. The MCTS area may be designated based on the range of the level indicated by the LoD, or an area including only refinement points excluding levels included in lower levels in each level indicated by the LoD may be designated as the MCTS area.

[0224] The encoding method according to the embodiments can encode a partial region (MCTS or subpicture) within a frame based on a LoD level and / or a refinement level, and generate syntax element(s) indicating a partial region relationship. The decoding method according to the embodiments can efficiently decode a partial region (MCTS or subpicture) within a frame including mesh data based on a LoD level and / or a refinement level, based on the syntax element(s) indicating a partial region relationship.

[0225] Figure 21 shows an example of specifying a quantized displacement vector transform coefficient packing area for each LoD according to embodiments.

[0226] The encoding / decoding method according to the embodiments may set a one-to-one correspondence between MCTS or subpictures and LoD levels, or may not set a one-to-one correspondence. Fig. 21 illustrates an example in which MCTS or subpictures and LoD levels are set in a one-to-one correspondence, where refinement level 3 may be designated as subpicture 0, refinement level 2 as subpicture 1, refinement level 1 as subpicture 2, and refinement level 0 as subpicture 3.

[0227] Figure 22 shows an example of specifying a quantized displacement vector transform coefficient packing area for each LoD according to embodiments.

[0228] Referring to Fig. 22, this is an example of a case where MCTS or subpicture and LoD level are not set in a one-to-one correspondence relationship, and refinement level 3 can be designated as subpicture 0, refinement level 2 as subpicture 1, and refinement levels 1 and 0 as subpicture 2. Areas for at least two or more refinement levels can be designated as one subpicture.

[0229] Referring to FIGS. 21 and 22, the encoding method according to the embodiments can encode a partial region (subpicture) within a frame based on a refinement level and generate syntax element(s) indicating a partial region relationship. The decoding method according to the embodiments can efficiently decode a partial region (subpicture) within a frame including mesh data based on a refinement level, based on the syntax element(s) indicating a partial region relationship.

[0230] Figure 23 shows displacement vector transform according to embodiments.

[0231] Fig. 23 illustrates the displacement vector transformation operation of the Fig. 17 encoder. According to an embodiment, the restoration displacement vector transformation coefficient may be stored in a buffer according to a reference structure, and the restoration displacement vector transformation coefficient (refDisCoeff) of the reference mesh to which the current mesh vertex is mapped may be used as a predictor of the current displacement vector transformation coefficient, thereby performing prediction using the following formula.

[0232] for (size_t v = 0; v < N ; v++){

[0233] for (size_t d =0; d< dim; d++){

[0234] disCoeff[v][d]=curdispCoeff[v][d]-refDispCoeff[v][d]

[0235] }

[0236] }

[0237] Displacement vector transform coefficient quantization can perform inverse quantization on the differential displacement vector transform coefficient (disCoeff) obtained by subtracting the predicted displacement vector transform coefficient (refDispCoeff) from the current displacement vector transform coefficient (curdispCoeff).

[0238] Figure 24 shows a lifting-based displacement vector transform according to embodiments.

[0239] Following Fig. 23, Fig. 24 describes an operation of converting a displacement vector based on a lifting method.

[0240] Displacement vector transformation unit: A displacement vector in an (x, y, z) or (n, t, bt) coordinate system can be transformed through the displacement vector transformation unit. In an embodiment, when a coordinate system transformation is performed into an (n, t, bt) coordinate system, a 1D scalar displacement vector of a normal (n) component is applied as an input of the displacement vector transformation unit, and transformation, quantization, and encoding can be performed on the displacement value of the normal component. The transformation may be a lifting transformation, a wavelet transformation, etc., depending on the embodiment. When a lifting transformation is performed, a displacement vector transformation can be performed through the embodiment of FIG. 24. The number of lifting transformations can be determined using the number of mesh subdivision levels (lodCount). The lifting transformation process can be performed in units of mesh subdivision levels. During the lifting transformation process, a lifting transformation prediction unit and a lifting transformation update unit can be performed.

[0241] Lifting transformation prediction part: The lifting transformation prediction part is the vertex of the kth subdivision level. When performing displacement vector prediction, t( or ) Vertex of the th subdivision level The displacement vector of the kth subdivision level can be used as a predictor to perform displacement vector prediction. In some embodiments, when performing displacement vector prediction, an average or distance-based weighted average prediction can be performed on n points near the current vertex based on connection information among vertices at a lower subdivision level than the current vertex. In some embodiments, the prediction can be performed based on the displacement vectors of n vertices used to generate the current vertex in the mesh subdivision step. A residual signal can be generated through the difference between the displacement vector of the subdivision level and the predicted displacement vector.

[0242] Lifting transformation update unit: The lifting transformation update unit can update the displacement vector of the vertex used for prediction through the residual signal generated by the lifting transformation prediction unit.

[0243] Lifting transformation update part: The lifting transformation update weight (updateWeight) can be derived using the vltp_log2_lifting_update_weight syntax. The lifting transformation update process can perform updates by sharing the same weight for each LoD level of the mesh, or can perform updates using different weights for each LoD level of the mesh. Depending on the embodiment, if adaptiveUpdateWeight, which determines whether to perform an adaptive update, is 0, the same update weight can be used for each LoD level, and if it is 1, different adaptive updates can be performed for each LoD level according to the characteristics of the LoD level.

[0244] Displacement vector transform coefficient quantization unit: Quantization is performed on the transform coefficients transformed through the displacement vector transform unit. Depending on the embodiment, the transform coefficients may be quantized through different quantization parameters for each axis, and the quantization parameter or scaling parameter may be derived by the encoder / decoder agreement to determine the quantization rate for each LoD level.

[0245] Fig. 25 shows a decoder according to embodiments.

[0246] A decoding device according to embodiments may be configured like the decoder of FIG. 25. The decoding device (decoder) may include memory and / or at least one processor. At least one processor may be configured to perform the operations of each component of FIG. 25. The decoder of FIG. 25 may perform the reverse process of the operation of the encoder of FIG. 21.

[0247] Motion Vector Decoding Unit: If the current mesh performs inter-frame prediction, motion vector decoding can be performed. Residual motion vectors are decoded at the vertex or subblock level through the motion vector bitstream, and previously decoded motion vectors are used as predictors to perform prediction based on connection information, which is then added to the residual motion vectors to decode the motion vectors.

[0248] Static mesh decoding unit: The static mesh decoding unit can restore the connection information, vertex geometry information, vertex texture coordinates, normal information, etc. of the base mesh.

[0249] Base Mesh Restoration Unit: If the current base mesh is encoded based on a reference mesh, the current base mesh can be restored by adding a motion vector to the reference base mesh and then performing inverse quantization. If the current base mesh is decoded through a static mesh encoding unit, inverse quantization is performed to generate a restored base mesh. Depending on the embodiment, the inverse quantization unit may be omitted.

[0250] Mesh subdivision unit: The mesh subdivision unit can generate additional vertices by performing subdivision on the base mesh. At this time, depending on the subdivision method, geometric information connection information, texture coordinate connection information, and texture coordinates can be implicitly derived and generated. The mesh subdivision unit can perform subdivision using a method such as mid-edge, Loop, Catmul&Clark, etc., depending on the embodiment. Mesh subdivision can be performed several times by user parameters or decoder / decoder agreement, and depending on the embodiment, the vertices of the base mesh , perform subdivision 1 to create a new vertex , …, the vertices generated by performing n-th subdivision When defined as can be defined as follows: = ∪ ∪, … , ∪

[0251] The mesh segmentation unit can perform segmentation as many times as the number of segmentations for the target LoD input by the user (or decoder settings). For example, if the target LoD is input as 1, the segmentation number can be derived as 1 and segmentation can be performed once. If the target LoD is input as 2, the segmentation number can be derived as 2 and segmentation can be performed twice.

[0252] Figure 26 shows the displacement vector coordinate system inverse transformation and normal vector derivation according to embodiments.

[0253] Displacement vector coordinate system inverse transformation unit: The displacement vector coordinate system inverse transformation unit can inversely transform the dequantized restored displacement vector into the (x, y, z) coordinate axes if the coordinate system transformation flag () parsed by sequence or GoF (group of frame) or frame or sub-mesh unit is 1. At this time, the normal vector per vertex is calculated based on the restored vertex position information of the restored base mesh, and the normal value of the newly generated vertex can be assigned by interpolating the normal vector of the restored base mesh calculated for the vertex additionally generated through the subdivision process (see Fig. 26 (a)). At this time, in the case of interpolation, the interpolation can be performed by averaging or distance-based weighting the normal information of the base mesh used for subdivision. According to an embodiment, after performing subdivision on the restored base mesh, the normal vector can be calculated for the vertex generated through the subdivision unit and the vertex of the base mesh (see Fig. 26 (b)). Using the computed normal vector per vertex, we can compute the tangential and bi-tangential vectors perpendicular to the normal vector and perform the inverse transformation of the displacement vector coordinate system using the following formula:

[0254]

[0255] Depending on the embodiment, it is always possible to perform coordinate system inversion without sending flags.

[0256] Mesh restoration unit: The mesh restoration unit calculates the vertex position information of the restoration mesh by adding the restoration displacement vector to the vertices generated through the subdivision process in the mesh subdivision unit.

[0257] Texture Map Decoding Unit: The texture map decoding unit can receive a texture map bitstream as input and decode the texture map. The texture map decoder can decode through a video decoder, a zero-run length decoder, an arithmetic decoder, etc. Depending on the embodiment, a color space conversion of the texture map can be performed.

[0258] Figure 27 shows displacement vector decoding according to embodiments.

[0259] Displacement vector transform coefficient decoding unit: The displacement vector transform coefficient decoding unit can perform displacement vector decoding through a 2D video decoder such as H.264, HEVC, VVC, etc., or decode through a zero run length decoder or an arithmetic decoder, etc. The displacement vector transform coefficient decoding method can be determined by a specific decoding method by a unit / decoder agreement, or can be determined by receiving the encoding method determined by the encoder as a flag or index (dispEncType). Displacement vector transform coefficient decoding methods may vary, and depending on the embodiment, one of {video codec-based decoding method, zero run-length decoding method}, {video codec-based decoding method, zero run-length decoding method}, {video codec-based decoding method, arithmetic decoding method}, video codec-based decoding method, zero run-length decoding method, and arithmetic decoding method may be determined through the dispEncType flag or index. Depending on the embodiment, the displacement vector transform coefficient decoding method may be determined according to a profile defined in the sub-decoder, and an index (profileToolsetIdx) indicating profile information may be transmitted so that the decoder may determine the displacement vector decoding method according to profileToolsetIdx. When the displacement vector decoding method is a video codec-based decoding method, the displacement vector transform coefficient depacking unit may be a process of depacking a packed displacement vector transform coefficient frame. In the displacement vector transform coefficient de-packing unit, the de-packing method can be derived in the same way as the de-packing unit / decoder, or the packing method can be transmitted and the decoder can determine the de-packing method. The de-packing method can be a raster-scan order or a rectangular shape, depending on the embodiment.

[0260] Displacement vector dequantization unit: The displacement vector dequantization unit can perform dequantization on displacement vectors. Depending on the embodiment, the transform coefficients can be quantized through different quantization parameters for each axis, and the quantization parameter or scaling parameter can be derived by the encoder / decoder agreement to determine the quantization rate for each LoD level.

[0261] Figure 28 shows a lifting-based displacement vector inverse transform according to embodiments.

[0262] Displacement vector inverse transform unit: The displacement vector inverse transform unit can inversely transform the transformation performed in the encoder. The inverse transform can be performed by lifting inverse transform, wavelet inverse transform, etc., depending on the embodiment. When lifting inverse transform is performed, displacement vector inverse transform can be performed through the embodiment of FIG. 28. The number of lifting inverse transforms can be determined using the number of mesh subdivision levels (lodCount).

[0263] When a target LoD is input from a user (or decoder setting), the number of lifting inverse transformations can be derived as many times as the number of subdivisions for the target LoD.

[0264] The lifting inverse transformation process can be performed at each mesh subdivision level. The lifting inverse transformation process can include a lifting inverse transformation prediction unit and a lifting inverse transformation update unit.

[0265] Lifting Inverse Transform Prediction Unit: The lifting inverse transform prediction unit can predict the displacement vector on which the lifting inverse transform update unit has been performed. The lifting inverse transform prediction unit is the vertex of the kth subdivision level. When performing displacement vector prediction, t(t <k또는 ) Vertex of the th subdivision level The displacement vector of the kth subdivision level can be predicted using the displacement vector as a predictor. In some embodiments, when predicting the displacement vector, an average or distance-based weighted average prediction can be performed on n points near the current vertex based on connection information among vertices at a lower subdivision level than the current vertex. In some embodiments, prediction can be performed based on the displacement vectors of n vertices used to generate the current vertex in the mesh subdivision step. The displacement vector of the vertex of the subdivision level can be restored by adding the predicted displacement vector and the parsed residual signal.

[0266] Lifting Inverse Transform Update Unit: The lifting inverse transform update unit can update the displacement vector of the vertex used for prediction through the parsed residual signal. The lifting inverse transform update weight (updateWeight) can be derived from the vltp_log2_lifting_update_weight syntax. The lifting inverse transform update process can perform updates by sharing the same weight for each LoD level of the mesh, or can perform updates using different weights for each LoD level of the mesh. Depending on the embodiment, if adaptiveUpdateWeight, which determines whether to perform an adaptive update, is 0, the same update weight can be used for each LoD level, and if it is 1, different adaptive updates can be performed depending on the characteristics of the LoD level.

[0267] Figure 29 shows geometry information syntax according to embodiments.

[0268] The encoding method according to the embodiments may encode the geometry of mesh data, generate syntax regarding the geometry information, and generate a bitstream including the encoded mesh data and syntax. The syntax may be transmitted via an SEI message.

[0269] The decoding method according to the embodiments can extract only a part of the bitstream of an area corresponding to a specific LoD level to be decoded among the areas packed by LoD level in the displacement vector (geometry of mesh data) bitstream based on the syntax of Figs. 29 to 30. The syntax for partial access by LoD is described below. The syntax element according to the embodiments can be defined in all syntax and semantics in the bitstream, and some syntax can be omitted.

[0270] For example, in the case of GVD data, a syntax for partial decoding of displacement vectors may be configured in the geometry information syntax for the V-DMC extension, or may be signaled as an SEI message.

[0271] The semantics for the geometry information syntax element in Figure 29 are as follows:

[0272] Number of geometry frames (gi_num_geometry_frames_minus1): This refers to the number of displacement vector frames.

[0273] Geometry Frame ID (gi_geometry_frame_id): This refers to the ID of the displacement vector frame.

[0274] Number of submesh (gi_number_of_submesh_minus1[k]): This refers to the number of submesh within the displacement vector frame whose ID is K.

[0275] Submesh ID (gi_submesh_id[k][i]): This refers to the ID of the ith submesh of the displacement vector frame whose ID is k.

[0276] Subdivision iteration count (gi_subdivision_iteration_count[ k ][ s ]): This refers to the number of subdivisions of the submesh with ID s within the displacement vector frame with ID k.

[0277] MCTS ID (gi_mcts_id[ k ][ s ][ j ]): This refers to the ID of the MCTS in which the displacement vector of the LoD level j of the sub-mesh of the ID s within the displacement vector frame of the ID k is packed.

[0278] Top-left tile index (gi_top_left_tile_idx[ k ][ s ][ j ]): This refers to the index of the tile located at the top left among the tiles packed with the displacement vector of LoD level j of the sub-mesh with ID s within the displacement vector frame with ID k.

[0279] Bottom-right tile index (gi_bottom_right_tile_idx[ k ][ s ][ j ]): This refers to the index of the tile located at the bottom right among the tiles packed with the displacement vector of LoD level j of the sub-mesh with ID s within the displacement vector frame with ID k.

[0280] Subpicture ID (gi_subpic_id[ k ][ s ][ j ]): This refers to the ID of the subpicture in which the displacement vector of the LoD level j of the submesh of the ID s within the displacement vector frame of the ID k is packed.

[0281] FIG. 30 illustrates a displacement partial extraction SEI payload syntax according to embodiments.

[0282] Number of displacement frames (pde_num_displacement_frames_minus1): Adding 1 to this value means the number of displacement vector frames.

[0283] Codec type index (pde_ codec_type_idx): This can indicate the video codec type of the displacement vector frame. If it is 0, it means that it is encoded with HEVC, and if it is 1, it means that it is encoded with VVC.

[0284] Number of submesh (pde_number_of_submesh_minus1): Adding 1 to this value means the number of submesh in the i-th displacement vector frame.

[0285] Submesh ID (pde_submesh_id[i][j]): This refers to the ID of the jth submesh of the ith displacement vector frame.

[0286] Subdivision iteration count (pde_subdivision_iteration_count[ i ][ j ]): This refers to the number of subdivisions of the jth submesh within the ith displacement vector frame.

[0287] MCTS ID (pde_mcts_id[ i ][ j ][ l ]): This refers to the ID of the MCTS in which the displacement vector of the jth sub-mesh in the ith displacement vector frame is packed with the LoD level l.

[0288] Top-left tile index (pde_top_left_tile_idx[ i ][j ][ l ]): This refers to the index of the tile located at the top left among the packed tiles of the displacement vector whose LoD level is l of the jth sub-mesh within the i-th displacement vector frame.

[0289] Bottom right tile index (pde_bottom_right_tile_idx[ i ][ j ][ l ]): This refers to the index of the tile located at the bottom right among the packed tiles of the displacement vector whose LoD level is l of the jth sub-mesh within the ith displacement vector frame.

[0290] Subpicture ID (pde_subpic_id[ i ][ j ][ l ]): This refers to the ID of the subpicture in which the displacement vector of the jth submesh in the ith displacement vector frame is packed with the LoD level l.

[0291] Figure 31 shows the LoD extraction information SEI payload syntax according to embodiments.

[0292] Extraction unit type index (pde_extractable_unit_type_idx): This can indicate an extraction unit at the video codec level. If it is 0, it means MCTS (Motion-constrained tile sets), and if it is 1, it means encoded as a subpicture.

[0293] Number of submesh (pde_number_of_submesh_minus1): Adding 1 to this value means the number of submesh.

[0294] Submesh ID (pde_submesh_id[i]): This refers to the ID of the i-th submesh.

[0295] Subdivision iteration count (pde_subdivision_iteration_count[ i ]): This refers to the number of subdivisions of the i-th submesh.

[0296] MCTS index (pde_mcts_idx[ i ][ j ]): When pde_extractable_unit_type_idx is 0 (encoded as MCTS), it means the index of the MCTS in which the displacement vector of the LoD level j of the i-th sub-mesh is packed.

[0297] Subpicture index (pde_subpic_idx[ i ][ j ]): When pde_extractable_unit_type_idx is 1 (encoded as subpicture), it means the index of the subpicture into which the displacement vector of the LoD level j of the i-th submesh is packed.

[0298] MCTS information set ID (mcts_info_sets_id[ i ][ j ]): may mean a set index of motion-constrained tile sets extraction information sets whose LoD level of the ith sub-mesh is j. Motion-constrained tile sets extraction information sets may mean MCTS extraction information sets defined in (Annex D.3.43 Motion-constrained tile sets extraction information sets SEI message semantics in ISO / IEC 23008-2). mcts_info_sets_id[ i ][ j ] may be signaled in a LoD extraction information SEI message or may be derived through a motion-constrained tile sets extraction information sets SEI message, depending on the embodiment. If mcts_info_sets_id[ i ][ j ] is signaled, the target MCTS extraction information set identifier (mcts_info_sets_id[ i ][ j ]) can be derived from the MCTS bitstream extraction process (as specified in Annex D.3.43 Motion-constrained tile sets extraction information sets SEI message semantics in ISO / IEC 23008-2). If mcts_info_sets_id[ i ][ j ] is not signaled, the target MCTS extraction information set identifier (as specified in Annex D.3.The target MCTS extraction information set identifier can be derived from the motion-constrained tile sets extraction information sets SEI message semantics in ISO / IEC 23008-2.

[0299] Fig. 32 shows a decoder according to embodiments.

[0300] An encoder according to embodiments may partially encode displacement vectors of mesh data by LoD and generate syntax for partial extraction. A decoder according to embodiments may be configured as a dynamic mesh content receiver (decoder) as shown in FIG. 32, and may perform the following procedure, for example, based on the operation of the mesh data decoder of FIG. 32. The decoder of FIG. 32 may be configured with a memory and / or at least one processor. At least one processor may be configured to perform the operations of each module of FIG. 32.

[0301] When information for partial extraction of displacement vector bitstreams per LoD level is signaled as an extension of the geometry information in the V3C parameter set:

[0302] 1) The stored and / or received dynamic mesh content passes through the delivery module and the file decapsulation file module and is output in a form similar to the dynamic mesh bitstream structure of Fig. 15.

[0303] 2) The bitstream parser inside the mesh data decoding module can parse the dynamic mesh content bitstream.

[0304] 3) The bitstream parser parses the V3C unit header and V3C unit payload that constitute the bitstream, and can obtain data corresponding to V3C_VPS (data of V3C parameter set (VPS)) and data corresponding to V3C_GVD (video sub_bitstream) of the unit type defined in Fig. 16.

[0305] 4) The receiver can obtain information for partial extraction from the displacement video bitstream by LoD level as described in the geometry information syntax of the GVD data in Fig. 29 through the geometry information VDMC extension (geometry_information_vdmc_extension) in the VPS obtained in the above process 3).

[0306] 5) The receiver can identify the encoded displacement vector data information to partially extract the displacement vector bitstream by LoD level from the bitstream of the dynamic mesh content prior to the direct decoding process of the displacement vector data through the processes 1) to 4) above.

[0307] When information for partial extraction of displacement vector bitstreams per LoD level is signaled as SEI messages:

[0308] 1) The stored and / or received dynamic mesh content passes through the delivery module and the file decapsulation module and can be output in a form similar to the dynamic mesh bitstream structure of FIG. 15.

[0309] 2) The bitstream parser inside the mesh data decoding module can parse the dynamic mesh content bitstream.

[0310] 3) The bitstream parser parses the V3C unit header and V3C unit payload that constitute the bitstream, and can obtain data (V3C parameter set (VPS) data) corresponding to the unit type V3C_VPS defined in Fig. 16 and data (video sub_bitstream) corresponding to V3C_GVD.

[0311] 4) The receiver can obtain information for partial extraction from a displacement video bitstream by LoD level through an SEI message as described in the displacement partial extraction SEI payload syntax of FIG. 30.

[0312] 5) The receiver can identify the encoded displacement vector data information to partially extract the displacement vector bitstream by LoD level from the bitstream of the dynamic mesh content prior to the direct decoding process of the displacement vector data through the processes 1) to 4) above.

[0313] When information for partial extraction of displacement vector bitstreams per LoD level is signaled as SEI messages:

[0314] 1) The stored and / or received dynamic mesh content is output as a dynamic mesh bitstream structure of FIG. 15 based on the delivery module and / or file decapsulator.

[0315] 2) The bitstream parser inside the mesh data decoding module can parse the dynamic mesh content bitstream.

[0316] 3) The bitstream parser parses the V3C unit header and V3C unit payload that constitute the bitstream, and can obtain data (V3C parameter set (VPS) data) corresponding to the unit type V3C_VPS defined in Fig. 16 and data (video sub-bitstream) corresponding to V3C_GVD.

[0317] 4) The decoder can obtain information for partial extraction from the displacement video bitstream for each LoD level through the SEI message as described in the displacement partial extraction SEI payload syntax (LoD_extraction_information) of FIG. 31.

[0318] 5) The decoder can identify the encoded displacement vector data information to partially extract the displacement vector bitstream by LoD level from the bitstream of the dynamic mesh content prior to the direct decoding process of the displacement vector data through the processes 1) to 4) described above.

[0319] 6) In the displacement vector video bitstream extraction process, a sub-video bitstream can be extracted by inputting an MCTS index or subpicture index corresponding to the user's target LoD into the bitstream extraction process according to the user's target LoD. The MCTS bitstream extraction process can extract a sub-bitstream corresponding to a specific MCTS through the process specified in (Annex D.3.43 Motion-constrained tile sets extraction information sets SEI message semantics in ISO / IEC 23008-2). The subpicture bitstream extraction process can extract a sub-bitstream corresponding to a specific subpicture through the process specified in (Annex C.7 Subpicture sub-bitstream extraction process in ISO / IEC 23090-3). Multiple extracted sub-bitstreams can be merged to generate a single sub-bitstream.

[0320] Figure 33 shows the relationship between refinement level and packing of frame areas according to embodiments.

[0321] When packing displacement data by LoD based on a rectangular shape, the encoder can pack in various orders because there is no separate constraint on the packing position within the frame. For example, the encoding method according to the embodiments can pack displacement vectors (displacement data) for each refinement level within the frame based on a rectangular shape, as shown in FIG. 33, in the case of a mesh with LoD level 3. Similarly, the decoding method according to the embodiments can unpack (obtain) displacement vectors for each refinement level within the frame.

[0322] LoD 0 may include refinement level 0, LoD 1 may include refinement levels 0 and 1, LoD 2 may include refinement levels 0, 1, and 2, and LoD 3 may include refinement levels 0, 1, 2, and 3.

[0323] In the case of packing as in Fig. 33, an example of mapping between LoD and mcts index when signaling mcts idx (or subpicture idx) by LoD is as in Fig. 34, and an example of mapping between refinement level and mcts index when signaling mcts idx by refinement level is as in Fig. 35.

[0324] Figure 34 shows an example of the configuration and signaling of a LoD star area according to embodiments.

[0325] In Fig. 34, when signaling the mcts index associated with LoD 2, the mcts indices of the areas associated with refinement levels 0, 1, and 2 must be signaled. At this time, when configuring the mcts area, since it can only be configured as a rectangular area, refinement levels 0 and 1 can be configured as one mcts, and refinement level 2 can be configured as one mcts, thereby dividing the area within the frame into a total of two mcts. At this time, two mcts indexes, mcts index 1, which is the identifier of the area associated with refinement levels 0 and 1, and mcts 2, which is the identifier of the area associated with refinement level 2, must be signaled, so multiple mcts indices corresponding to a specific LoD may need to be signaled.

[0326] Figure 35 shows an example of the configuration and signaling of areas by refinement level according to embodiments.

[0327] In Fig. 35, when signaling the associated mcts index for each refinement level, since each refinement level is packed into a rectangle, there can only be one associated mcts index for each refinement level. For example, in the case of rectangular packing, no matter where the displacement vector for each refinement level is packed within the frame, only one corresponding mcts index for each refinement level needs to be signaled, which has the effect of reducing signaling bits and facilitating mcts / subpicture configuration.

[0328] In other words, the encoding / decoding method according to the embodiments can configure and signal partial extraction regions for each refinement level. Compared to configuring regions based on LoD levels, configuring regions by refinement levels results in a different MCTS configuration method. For example, signaling by refinement level versus LoD can reduce the bit size for signaling information, and facilitate the MCTS (or subpicture) configuration method regardless of the packing position within the frame of displacement data.

[0329] Figure 36 shows an encoding method according to embodiments.

[0330] The encoding method according to the embodiments may include a step of encoding a base mesh of mesh data (S6300); a step of encoding a displacement of mesh data (S3610); and / or a step of encoding an attribute of mesh data (S3620).

[0331] The step of encoding displacement in the encoding step (S3610) includes: extracting displacement from an area related to MCTS (Motion-constrained Tile Sets), and the area may be related to a refinement level of LoD (level of detail) for a submesh of mesh data.

[0332] Vertices of mesh data are expressed based on LoD, and vertices included in the first level of LoD and not included in the second level of LoD can be included in the area. Here, the first level may mean a higher level, and the second level may mean a lower level. For example, in LoD 3 and LoD 2, a level excluding the vertices included in LoD 2 among the vertices included in LoD 3 may be referred to as refinement level 3. A level that includes points (vertices) that exist solely in the level indicated by the LoD index having the index of the refinement level may be referred to as a refinement level.

[0333] The step of encoding the displacement includes: extracting the displacement from a region with respect to a subpicture, wherein the region may be related to a refinement level of a level of detail (LoD) for the submesh of the mesh data.

[0334] The bitstream includes information indicating a unit for extracting displacement, information related to the number of sub-meshes of the base mesh of the mesh data, an ID of the sub-mesh, and information indicating the number of repetitions for subdivision of the sub-mesh, and the unit for extracting displacement may include at least one of an MCTS or a sub-picture.

[0335] The encoding method may be performed by an encoding device (encoder). The encoding device includes a memory; and at least one processor connected to the memory; and the at least one processor may be configured to: encode a base mesh of mesh data; encode a displacement of the mesh data; and encode an attribute of the mesh data.

[0336] Embodiments further include a computer-readable storage medium storing a bitstream generated by the method according to FIG. 36.

[0337] Embodiments further include a method comprising: obtaining a bitstream for mesh data, the bitstream being generated based on: encoding a base mesh of the mesh data; encoding a displacement of the mesh data; and encoding an attribute of the mesh data; and transmitting data including the bitstream.

[0338] Figure 37 shows a decryption method according to embodiments.

[0339] A decoding method according to embodiments may include a step of decoding a base mesh within a bitstream (S3700); a step of decoding a displacement within a bitstream (S3710); and / or a step of decoding an attribute within a bitstream (S3720).

[0340] Referring also to FIG. 20, with respect to a method for specifying and extracting an MCTS region based on a refinement level, the step of decoding displacement includes: extracting displacement from a region related to MCTS (Motion-constrained Tile Sets), wherein the region may be related to a refinement level of a level of detail (LoD) for a submesh of mesh data.

[0341] Referring to FIG. 20 together, the vertices of the mesh data are expressed based on LoD, and vertices included in the first level of LoD and not included in the second level of LoD may be included in the area. Here, the first level may mean a higher level, and the second level may mean a lower level. For example, in LoD 3 and LoD 2, a level excluding the vertices included in LoD 2 among the vertices included in LoD 3 may be referred to as refinement level 3. A level that includes points (vertices) that exist solely in the level indicated by the LoD index having the index of the refinement level may be referred to as a refinement level.

[0342] Referring also to FIG. 21, with respect to a method of specifying and extracting a subpicture region based on a refinement level, the step of decoding a displacement includes: extracting a displacement from a region related to a subpicture, wherein the region may be related to a refinement level of a level of detail (LoD) for a submesh of mesh data.

[0343] Referring to FIG. 31 together, the bitstream includes information indicating a unit for extracting displacement, information related to the number of sub-meshes of the base mesh of the mesh data, an ID of the sub-mesh, and information indicating the number of repetitions for subdivision of the sub-mesh, and the unit for extracting displacement may include at least one of an MCTS or a sub-picture.

[0344] Referring also to FIG. 31, with respect to a method for identifying an extractable region within a bitstream, the bitstream may further include an identifier of an MCTS for a region including displacement within a refinement level of a submesh, based on an MCTS of a unit for extracting displacement, or may further include an identifier of a subpicture for a region including displacement within a refinement level of a submesh, based on a subpicture of a unit for extracting displacement.

[0345] The decryption method may be performed by a decryption device (decoder). The decryption device includes a memory; and at least one processor connected to the memory; and the at least one processor may be configured to: decode a basemesh within a bitstream; decode a displacement within the bitstream; and decode an attribute within the bitstream.

[0346] The method and device according to the embodiments provide the following technical effects.

[0347] Due to the encoding / decoding methods of Figs. 36 and 37, the encoder according to the embodiments can encode displacement of mesh data into extractable regions, and the decoder can decode displacement of mesh data into extractable regions. In addition, by extracting and decoding a portion of the displacement vector bitstream up to a specific LoD level depending on the receiver status, network environment, etc., the geometric information (displacement) scalability function of dynamic mesh compression can be supported.

[0348] The embodiments have been described in terms of methods and / or devices, and the descriptions of methods and devices may be applied complementarily.

[0349] For the convenience of explanation, each drawing has been described separately, but it is also possible to design a new embodiment by combining the embodiments described in each drawing. In addition, designing a computer-readable recording medium having a program recorded thereon for executing the previously described embodiments, as needed by a person skilled in the art, also falls within the scope of the embodiments. The devices and methods according to the embodiments are not limited to the configurations and methods of the embodiments described above, but the embodiments may be configured by selectively combining all or part of the embodiments so that various modifications can be made. Although preferred embodiments of the embodiments have been illustrated and described, the embodiments are not limited to the specific embodiments described above, and various modifications can be made by a person skilled in the art to which the present invention pertains without departing from the gist of the embodiments claimed in the claims, and such modifications should not be understood individually from the technical idea or prospect of the embodiments.

[0350] The various components of the devices of the embodiments may be implemented by hardware, software, firmware, or a combination thereof. The various components of the embodiments may be implemented by a single chip, for example, a single hardware circuit. According to embodiments, the components according to the embodiments may be implemented by separate chips. According to embodiments, at least one of the components of the devices of the embodiments may be configured with one or more processors capable of executing one or more programs, and the one or more programs may perform, or include instructions for performing, one or more of the operations / methods according to the embodiments. The executable instructions for performing the methods / operations of the devices of the embodiments may be stored in non-transitory CRMs or other computer program products configured to be executed by one or more processors, or may be stored in temporary CRMs or other computer program products configured to be executed by one or more processors. In addition, the memory according to the embodiments may be used as a concept including not only volatile memory (e.g., RAM, etc.), but also non-volatile memory, flash memory, PROM, etc. Additionally, it may include implementations in the form of carrier waves, such as transmissions via the Internet. Furthermore, processor-readable recording media may be distributed across network-connected computer systems, allowing processor-readable code to be stored and executed in a distributed manner.

[0351] In this document, “ / ” and “,” are interpreted as “and / or”. For example, “A / B” is interpreted as “A and / or B”, and “A, B” is interpreted as “A and / or B”. Additionally, “A / B / C” means “at least one of A, B, and / or C”. Also, “A, B, C” means “at least one of A, B, and / or C”. Additionally, “or” in this document is interpreted as “and / or”. For example, “A or B” can mean 1) “A” only, 2) “B” only, or 3) “A and B”. In other words, “or” in this document can mean “additionally or alternatively”.

[0352] Terms such as "first," "second," etc. may be used to describe various components of the embodiments. However, the various components according to the embodiments should not be interpreted as limited by these terms. These terms are merely used to distinguish one component from another. For example, a first user input signal may be referred to as a "second user input signal." Similarly, a second user input signal may be referred to as a "first user input signal." The use of these terms should be interpreted as not departing from the scope of the various embodiments. Although "first user input signal" and "second user input signal" are both user input signals, they do not mean the same user input signals unless the context clearly indicates otherwise.

[0353] The terminology used to describe the embodiments is for the purpose of describing particular embodiments and is not intended to be limiting of the embodiments. As used in the description of the embodiments and in the claims, the singular is intended to include the plural unless the context clearly dictates otherwise. The expressions “and / or” are used to mean all possible combinations of terms. The expression “includes” describes the presence of features, numbers, steps, elements, and / or components, but does not mean that additional features, numbers, steps, elements, and / or components are not included. Conditional expressions such as “if” or “when” used to describe the embodiments are not intended to be limited to only optional cases. When a specific condition is satisfied, a related action is performed in response to a specific condition, or a related definition is intended to be interpreted.

[0354] Additionally, the operations according to the embodiments described in this document may be performed by a transceiver device including a memory and / or a processor according to the embodiments. The memory may store programs for processing / controlling the operations according to the embodiments, and the processor may control various operations described in this document. The processor may be referred to as a controller, etc. The operations according to the embodiments may be performed by firmware, software, and / or a combination thereof, and the firmware, software, and / or a combination thereof may be stored in the processor or in the memory.

[0355] Meanwhile, the operations according to the embodiments described above may be performed by a transmitting device and / or a receiving device according to the embodiments. The transmitting / receiving device may include a transmitting / receiving unit for transmitting and receiving media data, a memory for storing instructions (program code, algorithm, flowchart, and / or data) for a process according to the embodiments, and a processor for controlling the operations of the transmitting / receiving device.

[0356] The processor may be referred to as a controller or the like, and may correspond to, for example, hardware, software, and / or a combination thereof. The operations according to the above-described embodiments may be performed by the processor. Furthermore, the processor may be implemented as an encoder / decoder or the like for the operations of the above-described embodiments.

[0357] As described above, the relevant contents have been described in the best form for carrying out the embodiments.

[0358] As described above, the embodiments may be applied in whole or in part to a point cloud data transmission and reception device and system.

[0359] Those skilled in the art may make various changes or modifications to the embodiments within the scope of the embodiments.

[0360] Embodiments may include modifications / changes, which do not depart from the scope of the claims and their equivalents.

Claims

1. Step of decoding the base mesh in the bitstream; A step of decoding displacement within the bitstream; and A step of decoding an attribute within the bitstream; comprising: How to decrypt.

2. In paragraph 1, The steps to decode the above displacement are: A step of extracting the above displacement from the area of ​​MCTS (Motion-constrained Tile Sets), The above area is related to the refinement level of the LoD (level of detail) for the submesh of the above mesh data. How to decrypt.

3. In paragraph 2, The vertices of the above mesh data are expressed based on the LoD, Vertices included in the first level of the above LoD and not included in the second level, which is a lower level of the first level, are included in the above area. How to decrypt.

4. In paragraph 1, The steps to decode the above displacement are: comprising a step of extracting the displacement from an area related to the subpicture, The above area is related to the refinement level of the LoD (level of detail) for the submesh of the above mesh data. How to decrypt.

5. In paragraph 2, The above bitstream is Information indicating the unit from which the above displacement is extracted, Information related to the number of sub-meshes of the base mesh of the above mesh data, The ID of the above submesh, Contains information indicating the number of repetitions for the subdivision of the above submesh, The unit for extracting the displacement includes at least one of MCTS or subpicture. How to decrypt.

6. In paragraph 5, The above bitstream is Based on the MCTS of the unit extracting the displacement, further include an identifier of the MCTS for the area containing the displacement within the refinement level of the submesh, or Based on the subpicture of the unit extracting the displacement, further including an identifier of a subpicture for an area including the displacement within the refinement level of the submesh, How to decrypt.

7. Memory; and At least one processor connected to the memory; wherein the at least one processor comprises: Decode the basemesh within the bitstream; Decoding displacements within the above bitstream; and configured to decode an attribute within the above bitstream; Decryption device.

8. Step of encoding the base mesh of mesh data; a step of encoding the displacement of the above mesh data; and A step of encoding attributes of the above mesh data; comprising: Encoding method.

9. In paragraph 8, The steps for encoding the above displacement are: A step of extracting the above displacement from the area of ​​MCTS (Motion-constrained Tile Sets), The above area is related to the refinement level of the LoD (level of detail) for the submesh of the above mesh data. Encoding method.

10. In paragraph 9, The vertices of the above mesh data are expressed based on the LoD, Vertices included in the first level of the above LoD and not included in the second level, which is a lower level of the first level, are included in the above area. Encoding method.

11. In paragraph 7, The steps for encoding the above displacement are: comprising a step of extracting the displacement from an area related to the subpicture, The above area is related to the refinement level of the LoD (level of detail) for the submesh of the above mesh data. Encoding method.

12. In paragraph 9, The above bitstream is Information indicating the unit from which the above displacement is extracted, Information related to the number of sub-meshes of the base mesh of the above mesh data, The ID of the above submesh, Contains information indicating the number of repetitions for the subdivision of the above submesh, The unit for extracting the displacement includes at least one of MCTS or subpicture. Encoding method.

13. Memory; and At least one processor connected to the memory; wherein the at least one processor comprises: Encode the base mesh of mesh data; Encoding the displacement of the above mesh data; and Encoding attributes of the above mesh data; configured to do so; Encoding device.

14. A computer-readable storage medium storing a bitstream generated by the method according to Article 8.

15. Step of obtaining bitstream for mesh data, The bitstream is generated based on the steps of encoding a base mesh of the mesh data; encoding a displacement of the mesh data; and encoding an attribute of the mesh data; and A method comprising the step of transmitting data including the bitstream.

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