3d data transmission device, 3d data transmission method, 3d data reception device, and 3d data reception method

Abstract

A 3D data transmission method according to an embodiment may comprise the steps of: pre-processing input mesh data; encoding the preprocessed grid data; and transmitting a bitstream including the encoded mesh data.

Description

Technical Field

[0001] Embodiments provide a method for providing 3D content to provide users with various services such as virtual reality (VR), augmented reality (AR), mixed reality (MR), and self-driving services. Background Art

[0002] Point cloud data or mesh data in 3D content is a collection of points in 3D space. However, due to the large number of points in 3D space, it is difficult to create point cloud data or mesh data.

[0003] In other words, a large throughput is required to transmit and receive 3D data (eg, point cloud or mesh data) having a considerable number of points. Summary of the invention

[0004] Technical issues

[0005] An object of the present disclosure is to provide an apparatus and method for efficiently transmitting and receiving mesh data to solve the above-mentioned problems.

[0006] Another object of the present disclosure is to provide an apparatus and method for solving delay and encoding / decoding complexity of mesh data.

[0007] The embodiments are not limited to the above-mentioned purposes, and the scope of the embodiments can be extended to other purposes that can be inferred by those skilled in the art based on the entire content of the present disclosure.

[0008] Technical Solution

[0009] To achieve these objectives and other advantages and in accordance with the purposes of the present invention, as embodied and broadly described herein, a method for transmitting three-dimensional (3D) data may include the steps of: preprocessing input mesh data; encoding the preprocessed mesh data; and transmitting a bitstream containing the encoded mesh data.

[0010] According to an embodiment, preprocessing may include: generating simplified mesh data by decimate input mesh data; generating texture coordinates of each vertex in the simplified mesh data; and subdividing the simplified mesh data with the texture coordinates, and then generating fitting subdivided mesh data similar to the input mesh data by fitting.

[0011] According to an embodiment, the generation of texture coordinates may include: segmenting polygons or vertices constituting the simplified mesh data by combining polygons or vertices having similar characteristics based on the characteristics of the polygons or vertices of the simplified mesh data; generating a mesh patch of the current frame based on a set of segmented polygons or vertices; and packing the mesh patch of the current frame onto a two-dimensional (2D) image based on a result of packing the mesh patch of a previous frame, and generating texture coordinates of each vertex of the simplified mesh data.

[0012] According to an embodiment, packing may include: determining whether a previous frame has a grid patch that matches a current grid patch of a current frame; and based on determining that the previous frame has a matching grid patch, determining a mapping position of the current grid patch on a 2D image based on a mapping position of the matching grid patch in the previous frame; and packing the current grid patch to the determined mapping position on the 2D image.

[0013] According to an embodiment, the current mesh patch may be packed onto the 2D image to have the same or close mapping position as the matching mesh patch in the previous frame.

[0014] According to an embodiment, mesh patches of the current frame corresponding to matching mesh patches in the previous frame may be first packed onto the 2D image.

[0015] According to an embodiment, determining whether the previous frame has a matching mesh patch may include determining that the mesh patch of the previous frame matches the current mesh patch based on the mesh patch of the previous frame being in the same orientation as the current mesh patch and having a similar number of polygons and / or vertices as the current mesh patch.

[0016] According to an embodiment, encoding may include regenerating texture coordinates based on texture coordinates of respective vertices in simplified mesh data and texture coordinates of respective vertices in input mesh data, and performing video encoding.

[0017] According to an embodiment, an apparatus for transmitting 3D data may include: a preprocessor configured to preprocess input mesh data; an encoder configured to encode the preprocessed mesh data; and a transmitter configured to transmit a bitstream including the encoded mesh data.

[0018] According to an embodiment, the preprocessor may include: a mesh simplification unit, which is configured to generate simplified mesh data by simplifying input mesh data; a parameterization unit, which is configured to generate texture coordinates of each vertex in the simplified mesh data; and a fitting subdivision surface unit, which is configured to subdivide the simplified mesh data with texture coordinates and then generate fitting subdivision mesh data similar to the input mesh data by fitting.

[0019] According to an embodiment, the parameterization unit may include: a polygon / vertex segmentation unit, which is configured to segment polygons or vertices constituting simplified mesh data by combining polygons or vertices with similar characteristics based on the characteristics of the polygons or vertices of the simplified mesh data; a mesh patch segmentation unit, which is configured to generate a mesh patch of a current frame based on a set of segmented polygons or vertices; and a mesh patch packer, which is configured to pack the mesh patch of the current frame onto a two-dimensional (2D) image based on the result of packing the mesh patch of the previous frame, and generate texture coordinates of each vertex of the simplified mesh data.

[0020] According to an embodiment, the grid patch packer may perform operations that may include: determining whether a previous frame has a grid patch that matches a current grid patch of a current frame; and based on determining that the previous frame has a matching grid patch, determining a mapping position of the current grid patch on the 2D image based on a mapping position of the matching grid patch in the previous frame; and packing the current grid patch to the determined mapping position on the 2D image.

[0021] According to an embodiment, the mesh patch packing unit may pack the current mesh patch onto the 2D image to have the same or close mapping position as the matching mesh patch in the previous frame.

[0022] According to an embodiment, the mesh patch packing unit may first pack mesh patches of the current frame corresponding to matching mesh patches in the previous frame onto the 2D image.

[0023] According to an embodiment, the mesh patch packer may determine that the mesh patch of the previous frame matches the current mesh patch based on the mesh patch of the previous frame being in the same orientation as the current mesh patch and having a similar number of polygons and / or vertices as the current mesh patch.

[0024] According to an embodiment, the encoder may regenerate texture coordinates based on texture coordinates of each vertex in the simplified mesh data and texture coordinates of each vertex in the input mesh data, and perform video encoding.

[0025] Beneficial Effects

[0026] According to an embodiment, a 3D data transmitting method, a 3D data transmitting apparatus, a 3D data receiving method, and a 3D data receiving apparatus may provide high-quality 3D services.

[0027] According to an embodiment, a 3D data transmitting method, a 3D data transmitting apparatus, a 3D data receiving method, and a 3D data receiving apparatus may implement various video codec schemes.

[0028] According to an embodiment, a 3D data transmitting method, a 3D data transmitting apparatus, a 3D data receiving method, and a 3D data receiving apparatus may support general 3D content, for example, for autonomous driving services.

[0029] According to an embodiment, a 3D data transmission method and a 3D data transmission device can regenerate a texture map with high image correlation by reflecting the image similarity between frames when generating texture coordinates of a simplified mesh. Therefore, they can improve the compression performance of the dynamic mesh of V-Mesh, and in particular improve the compression performance of the texture map video of the mesh. In addition, a user may be allowed to use fewer resources to store, utilize and send a bitstream generated after the compression encoder obtains mesh data using a texture map with high image correlation between frames, and store and utilize the bitstream on the receiving side. As a result, the cost associated with using mesh content in media and communication systems can be reduced, and the scope of applications utilizing mesh content can be effectively expanded. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings are included to provide a further understanding of the present disclosure and are incorporated into and constitute a part of this application. The accompanying drawings illustrate embodiments of the present disclosure and together with the description are used to illustrate the principles of the present disclosure. In order to better understand the various embodiments described below, reference should be made to the description of the following embodiments in conjunction with the accompanying drawings. The same reference numerals will be used throughout the drawings to represent the same or similar parts. In the drawings:

[0031] Figure 1 A system for providing dynamic grid content according to an embodiment is shown;

[0032] Figure 2 A V-MESH compression method according to an embodiment is shown;

[0033] Figure 3 illustrates pre-processing in V-MESH compression according to an embodiment;

[0034] Figure 4 An edge midpoint subdivision method according to an embodiment is shown;

[0035] Figure 5 shows a displacement generation process according to an embodiment;

[0036] Figure 6 FIG. 1 shows an intra-frame encoding process of V-MESH data according to an embodiment;

[0037] Figure 7 FIG. 1 shows an inter-frame encoding process of V-MESH data according to an embodiment;

[0038] Figure 8 The lifting transformation process of displacement according to the embodiment is shown;

[0039] Fig. 9 shows a process of packing transform coefficients into a 2D image according to an embodiment;

[0040] Fig.10 illustrates the attribute transfer process in the V-MESH compression method according to an embodiment;

[0041] Fig.11 FIG. 1 shows an intra-frame decoding process of V-MESH data according to an embodiment;

[0042] Fig.12 FIG. 1 shows an inter-frame decoding process of V-MESH data according to an embodiment;

[0043] Fig.13 A mesh data transmission device according to an embodiment is shown;

[0044] Fig.14 A mesh data receiving device according to an embodiment is shown;

[0045] Fig.15 shows an example of a regenerated texture map video according to an embodiment;

[0046] Fig.16 is an example detailed block diagram of a parameterization unit according to an embodiment;

[0047] Fig.17 is a flow chart illustrating an example parameterization method according to an embodiment;

[0048] Fig.18 is a flow chart illustrating an example mesh patch packing method according to an embodiment;

[0049] Fig.19 shows an example of a mapped mesh patch constituting a simplified mesh mapped onto a 2D image according to an embodiment;

[0050] Fig. 20 Another example of reconstructing a texture map video according to an embodiment is shown;

[0051] Fig.21 is a flowchart illustrating an example mesh data transmission method according to an embodiment; and

[0052] Fig. 22 is a flow chart illustrating an example mesh data receiving method according to an embodiment. DETAILED DESCRIPTION

[0053] Reference will now be made in detail to preferred embodiments of the present disclosure, examples of which are shown in the accompanying drawings. The detailed description given below with reference to the accompanying drawings is intended to illustrate exemplary embodiments of the present disclosure, rather than to illustrate the only embodiments that can be implemented according to the present disclosure. The following detailed description includes specific details in order to provide a thorough understanding of the present disclosure. However, it will be apparent to those skilled in the art that the present disclosure can be practiced without these specific details.

[0054] Although most of the terms used in the present disclosure are selected from general terms widely used in the art, some terms are arbitrarily selected by the applicant, and their meanings are explained in detail in the following description as needed. Therefore, the present disclosure should be understood based on the intended meanings of the terms rather than their simple names or meanings.

[0055] With recent advances in 3D data modeling and rendering technology, active research has been conducted on generating and processing 3D data across various fields, including virtual reality (VR), augmented reality (AR), autonomous driving, computer-aided design (CAD) / computer-aided manufacturing (CAM), and geographic information systems (GIS). 3D data can be represented as a point cloud or a mesh according to a representation format. The mesh consists of geographic information indicating the coordinates of each vertex or point, connection information indicating the connections between vertices, a texture map representing color information about the mesh surface as 2D image data, and texture coordinates indicating mapping information between the mesh surface and the texture map. In the present disclosure, a mesh is defined as a dynamic mesh when at least one element constituting the mesh changes over time, and is defined as a static mesh when it does not change.

[0056] Compared to 2D image data, dynamic mesh data involves significantly larger amounts of element data to represent the mesh. As a result, techniques have been developed for efficiently compressing large amounts of mesh data to store and transmit the data.

[0057] Figure 1 A system for providing dynamic grid content according to an embodiment is shown.

[0058] Figure 1 The system in the embodiment includes a sending device 100 and a receiving device 110. The sending device 100 may include a grid video acquisition unit 101, a grid video encoder 102, a file / segment encapsulator 103, and a sender 104. The receiving device 110 may include a receiver 111, a file / segment decapsulator 112, a grid video decoder 113, and a renderer 114. Figure 1The components in the embodiment may correspond to hardware, software, a processor and / or a combination thereof. In the following description, the mesh data transmitting device according to the embodiment may be interpreted as referring to the 3D data transmitting device or the transmitting device 100, or to the mesh video encoder (hereinafter referred to as the encoder) 102. The mesh data receiving device according to the embodiment may be interpreted as referring to the 3D data receiving device or the receiving device 110, or to the mesh video decoder (hereinafter referred to as the decoder) 113.

[0059] Figure 1 The system can perform video-based dynamic mesh compression and decompression.

[0060] With the advancement of 3D capture, modeling and rendering, users are allowed to access various forms of 3D content (e.g., AR, XR, metaverse and holograms) across multiple platforms and devices. 3D content is becoming more and more complex and realistic in its object representation to provide an immersive experience for users. However, for the generation and use of 3D models, a significant amount of data is required. Among various types of 3D content, 3D meshes are widely used for efficient data utilization and realistic object representation. An embodiment includes a series of processing steps in a system using mesh content.

[0061] First, the method of compressing dynamic mesh data starts with the video-based point cloud compression (V-PCC) standard technology for point cloud data. Point cloud data is data with color information in the coordinates (X, Y, Z) of the vertex (or point). In the present disclosure, the vertex coordinates (i.e., position information) are referred to as geometric information, and the color information about the vertex is referred to as attribute information. The geometric information and attribute information are collectively referred to as vertex information or point cloud data. Mesh data refers to vertex information including connection information between vertices. The content may be initially created in the form of mesh data. Alternatively, connection information may be added to the point cloud data, and the point cloud data may be transformed into mesh data.

[0062] Currently, the MPEG standard group defines two data types for dynamic mesh data: Category 1 mesh data having a texture map as color information and Category 2 mesh data having vertex colors as color information.

[0063] Standardization of grid encoding for Category 1 data is currently underway, with standardization of Category 2 data expected to follow. Figure 1 As shown, the overall process for providing grid content services may include acquisition, encoding, transmission, decoding, rendering and / or feedback processes.

[0064] In order to provide mesh content services, 3D data acquired by multiple cameras or special cameras can be processed into a mesh data type through a series of steps to generate a video. The generated mesh video can be sent through a series of operations, and the receiving side can process the received data back into a mesh video for rendering. Through this process, the mesh video can be provided to the user, allowing the user to interactively utilize the mesh content according to his or her intention.

[0065] like Figure 1 As shown, the grid compression system may include a sending device 100 and a receiving device 110. The sending device 100 may encode the grid video to output a bit stream, which may be transmitted to the receiving device 110 via a digital storage medium or a network in the form of a file or a stream (stream segment). The digital storage medium may include various storage media, such as USB, SD, CD, DVD, Blu-ray, HDD, and SSD.

[0066] In the transmitting device 100, the encoder may be referred to as a grid video / image / picture / frame encoding device. In the receiving device 110, the decoder may be referred to as a grid video / image / picture / frame decoding device. The transmitter may be included in a grid video encoder and the receiver may be included in a grid video decoder. The renderer 114 may include a display, and the renderer and / or the display may be configured as a separate device or an external component. The transmitting device 100 and the receiving device 110 may also include a separate internal or external module / unit / component for the feedback process.

[0067] Mesh data uses multiple polygons to represent the surface of an object. Each polygon is defined by vertices in 3D space and connection information indicating how the vertices are connected. In addition, vertex attributes such as color and normal vectors may be included in the data. Mapping information that allows the mesh surface to be mapped onto a 2D plane may also be included in the mesh attributes. The mapping is typically described using a set of parametric coordinates associated with the mesh vertices (called UV coordinates or texture coordinates). The mesh contains a 2D attribute map that can be used to store high-resolution attribute information such as textures, normals, and displacements. Here, displacement can be used interchangeably with displacement information or displacement vectors.

[0068] The mesh video acquisition unit 101 may include processing the 3D object data acquired by a camera or the like into a mesh data type having the above-mentioned attributes through a series of operations, and generating a video composed of the mesh data. In the mesh video, the attributes of the mesh (e.g., vertices, polygons, connections between vertices, colors, and normals) may change over time. The mesh video having attributes and connection information that change over time is called a dynamic mesh video.

[0069] The grid video encoder 102 can encode the input grid video into one or more video streams. The video may contain multiple frames, and each frame may correspond to a still image / picture. In the present disclosure, the grid video may include a grid image / frame / picture. The term "grid video" can be used interchangeably with the grid image / frame / picture. The grid video encoder 102 can perform a video-based dynamic grid (V-Mesh) compression process. For compression and coding efficiency, the grid video encoder 102 can perform a series of processes such as prediction, transformation, quantization and entropy coding. The encoded data (encoded video / image information) can be output in the form of a bitstream.

[0070] The file / segment encapsulation module 103 can encapsulate the encoded grid video data and / or grid video related metadata in the form of a file or the like. The grid video related metadata can be received from a metadata processor. The metadata processing unit may be included in the grid video encoder 102, or may be configured as a separate component / module. The file / segment encapsulation module 103 can encapsulate the data into a file format such as ISOBMFF, or process it into a form such as a DASH segment. According to an embodiment, the file / segment encapsulator 103 may include grid video related metadata in a file format. For example, the grid video metadata may be included in boxes at various levels in the ISOBMFF file format, or as data on a separate track in a file. In some embodiments, the file / segment encapsulator 103 may encapsulate the grid video related metadata into a file.

[0071] The transmission processor may apply processing to the encapsulated mesh video data based on the file format for transmission. The transmission processor may be included in the transmitter 104 or implemented as a separate component / module. The transmission processor may process the mesh video data according to any transmission protocol. The processing for transmission may include transmission processing via a broadcast network and transmission processing via broadband. In some embodiments, the transmission processor may receive mesh video related metadata and mesh video data from a metadata processor and process it for transmission.

[0072] The transmitter 104 may transmit the encoded video / image information or data output in the form of a bit stream to the receiver 111 of the receiving device 110 via a digital storage medium or a network in the form of a file or stream. The digital storage medium may include various storage media, such as USB, SD, CD, DVD, Blu-ray, HDD, and SSD. The transmitter 104 may include an element for generating a media file in a predetermined file format, and may include an element for transmission via a broadcast / communication network. The receiver 111 may extract the bit stream and transmit it to a decoding device.

[0073] The receiver 111 may receive the mesh video data transmitted by the mesh data transmitting device. The receiver 111 may receive the mesh video data via a broadcast network or a broadband network, or may receive the mesh video data via a digital storage medium, depending on a channel used for transmission.

[0074] The receiving processor may perform processing on the received mesh video data according to the transmission protocol. The receiving processor may be included in the receiver 111, or may be configured as a separate component / module. In order to correspond to the processing performed for transmission on the transmitting side, the receiving processor may perform the inverse process of the operation of the above-mentioned transmitting processor. The receiving processor may transmit the acquired mesh video data to the file / segment decapsulator 112 and transmit the acquired mesh video related metadata to the metadata parser. The mesh video related metadata acquired by the receiving processor may be in the form of a signaling table.

[0075] The file / segment decapsulator 112 can decapsulate the grid video data in the form of a file received from the receiving processor. The file / segment decapsulator 112 can decapsulate the file etc. according to ISOBMFF etc. to obtain a grid video bitstream or grid video related metadata (metadata bitstream). The obtained grid video bitstream can be transmitted to the grid video decoder 113, and the obtained grid video related metadata (metadata bitstream) can be transmitted to the metadata processor. The grid video bitstream may include metadata (metadata bitstream). The metadata processor may be included in the grid video decoder 113, or may be configured as a separate component / module. The grid video related metadata obtained by the file / segment decapsulator 112 may be in the form of a box or track in the file format. When necessary, the file / segment decapsulator 112 may receive the metadata required for decapsulation from the metadata processor. The grid video related metadata may be transmitted to the grid video decoder 113 for use in the grid video decoding process, or transmitted to the renderer 114 for use in the grid video rendering process.

[0076] The grid video decoder 113 may receive an input bitstream and perform an inverse operation corresponding to the operation of the grid video encoder 102 to decode the video / image. The decoded grid video / image may be displayed through a display of the renderer 114. The user may view all or part of the rendering result through a VR / AR display, a general display, etc.

[0077] The feedback process may include sending various types of feedback information that may be obtained during the rendering / display operation to a decoder on the sending side or the receiving side. The feedback process may provide interactivity when consuming the mesh video. In some embodiments, the feedback process may include sending head orientation information, viewport information indicating the area the user is currently viewing, etc. In some embodiments, the user may interact with objects implemented in the VR / AR / MR / autonomous driving environment. In this case, information related to the interaction may be transmitted to the sending side or the service provider during the feedback process. In some embodiments, the feedback process may be skipped.

[0078] The head orientation information may refer to information about the user's head position, angle, movement, etc. Based on this information, information about the area within the grid video that the user is currently viewing (ie, viewport information) may be calculated.

[0079] The viewport information may be information about the area of ​​the grid video that the user is currently viewing. Based on this information, gaze analysis may be performed to determine how the user consumes the grid video, how long the user looks at a specific area of ​​the grid video, etc. Gaze analysis may be performed on the receiving side, and the results may be transmitted to the sending side via a feedback channel. Devices such as VR / AR / MR displays may extract the viewport area based on the user's head position / orientation, the vertical or horizontal FOV supported by the device, etc.

[0080] In some embodiments, the feedback information may not only be transmitted to the transmitter, but also consumed on the receiving side. In other words, operations such as decoding and rendering may be performed on the receiving side based on the feedback information. For example, based on the head orientation information and / or the viewport information, only the grid video of the area currently being viewed by the user may be preferentially decoded and rendered.

[0081] The present disclosure relates to implementations of dynamic mesh video compression as described above. The methods / implementations disclosed herein can be applied to the Video-Based Dynamic Mesh Compression (V-Mesh) standard of the Moving Picture Experts Group (MPEG) or any next-generation video / image coding standard. Dynamic mesh video compression is a method for processing mesh connectivity information and attributes that vary over time. It can perform lossy and lossless compression for various applications such as real-time communications, storage, free viewpoint video, and AR / VR.

[0082] The dynamic mesh video compression method described below is based on the V-mesh method of MPEG.

[0083] In the present disclosure, a picture / frame may generally refer to a unit representing one image at a specific time.

[0084] A pixel or a picture element may refer to the smallest unit constituting a picture (or video). In addition, the term "sample" may be used as a term corresponding to a pixel. A sample may generally indicate a pixel or a pixel value. It may indicate only a pixel / pixel value of a luma component, or may indicate only a pixel / pixel value of a chroma component, or may indicate only a pixel / pixel value of a depth component.

[0085] A unit may represent a basic unit of image processing. A unit may include at least one of a specific area of ​​a picture and information related to the area. In some cases, the term unit may be used interchangeably with terms such as block or area. Typically, an M×N block may include a set (or array) of samples (or sample array) or transform coefficients consisting of M columns and N rows.

[0086] As mentioned above, Figure 1 The encoding process is performed as follows.

[0087] In other words, the video-based dynamic mesh compression (V-Mesh) compression method can provide a method for compressing dynamic mesh video data based on a 2D video codec (e.g., High Efficiency Video Surface (HEVC) and Versatile Video Coding (VVC)). In the V-Mesh compression process, the following data is received as input and compressed.

[0088] Input mesh: includes the 3D coordinates of the vertices that make up the mesh, normal information about each vertex, mapping information for mapping the mesh surface to a 2D plane, and connections between the vertices that make up the surface. The mesh surface can be represented by triangles or other polygons, and the connection information between the vertices that make up the surface is stored according to a predetermined shape. The input mesh can be stored in the OBJ file format.

[0089] Attribute map (texture map is also used interchangeably below): contains information about the attributes of the mesh (color, normal, displacement, etc.), and stores the data in the form of a mapping of the mesh surface to a 2D image. The mapping that indicates which part of the mesh (surface or vertex) corresponds to each piece of data in the attribute map is based on the mapping information contained in the input mesh. Since the attribute map has data about each frame of the mesh video, it can also be called an attribute map video. The attribute map in the V-Mesh compression method mainly contains color information about the mesh and is stored in an image file format (PNG, BMP, etc.).

[0090] Material library file: Contains information about the material properties used in the mesh, especially information linking the input mesh to the corresponding property map. It is stored in the Wavefront Material Template Library (MTL) file format.

[0091] In the V-Mesh compression method, the following data and information may be generated through the compression process.

[0092] Base Mesh: Objects in the input mesh are represented using the minimum number of vertices determined according to user criteria by simplifying the input mesh through a preprocessing process.

[0093] Displacement: Used to represent the displacement information of the input mesh as similarly as possible to the base mesh, expressed in 3D coordinates.

[0094] Atlas information: Metadata required to reconstruct a mesh using base mesh, displacement and attribute map information. It can be used to generate and use sub-units of a mesh (sub-meshes, patches, etc.).

[0095] Reference Figures 2 to 7 Describes the method of encoding mesh position information (or vertex position information), see Figures 6 to 10 etc. describe a method of reconstructing grid position information to encode attribute information (attribute map).

[0096] Figure 2 A V-MESH compression method according to an embodiment is shown.

[0097] Figure 2 Show Figure 1 The encoding process may include a preprocessing process and an encoding process. Figure 2 As shown, Figure 1 The grid video encoder 102 may include a preprocessor 200 and an encoder 201. In addition, Figure 1 The sending device can be broadly called an encoder. Figure 1 The grid video encoder 102 may be referred to as an encoder. Figure 2 As shown, the V-Mesh compression method may include preprocessing 200 and encoding 201 . Figure 2 The preprocessor 200 may be located at Figure 2 The front end of the encoder 201. Figure 2 The pre-processor 200 and the encoder 201 may be referred to as a single encoder.

[0098] The preprocessor 200 may receive a static or dynamic mesh (M(i)) and / or an attribute map (A(i)). The preprocessor 200 may generate a base mesh m(i) and / or a displacement d(i) by preprocessing. The preprocessor 200 may receive feedback information from the encoder 201, and may generate a base mesh and / or a displacement based on the feedback information.

[0099] The encoder 201 may receive a base grid m(i), a displacement d(i), a static or dynamic grid M(i), and / or an attribute map A(i). In the present disclosure, at least one of the base grid m(i), the displacement d(i), the static or dynamic grid M(i), and / or the attribute map A(i) may be referred to herein as grid-related data. The encoder 201 may encode the grid-related data to generate a compressed bitstream.

[0100] Figure 3 Preprocessing in V-MESH compression according to an embodiment is shown.

[0101] Figure 3 Show Figure 2 The configuration and operation of the preprocessor. Figure 3 In the example, the input mesh may include a static or dynamic mesh M(i) and / or an attribute map A(i). The input mesh may also include 3D coordinates of vertices constituting the mesh, normal information about each vertex, mapping information for mapping the mesh surface to a 2D plane, and connection information between vertices constituting the surface.

[0102] Figure 3 200. The process of performing preprocessing on an input mesh is shown. Preprocessing 200 may include four operations: 1) Group of Frames (GoF) generation, 2) mesh simplification, 3) UV parameterization, and 4) fitting subdivision surface (300). According to an embodiment, GoF generation may be referred to as a GoF generation process or a GoF generator, mesh simplification may be referred to as a mesh simplification process or a mesh simplification part, UV parameterization may be referred to as a UV parameterization process or a UV parameterization part, and fitting subdivision surface may be referred to as a fitting subdivision surface process or a fitting subdivision surface part. The preprocessor 200 may generate a displacement and / or base mesh from the received input mesh and transmit it to the encoder 201. The preprocessor 200 may transmit GoF information related to GoF generation to the encoder 201.

[0103] Below, describe Figure 3 of each operation.

[0104] GoF generation: The process of generating a reference structure of mesh data. When the mesh of the previous frame and the current mesh have the same number of vertices, the same number of texture coordinates, the same vertex connection information, and the same texture coordinate connection information, the previous frame can be set as a reference frame. In other words, if only the vertex coordinate values ​​are different between the current input mesh and the reference input mesh, the encoder 201 can perform inter-frame encoding. Otherwise, it performs intra-frame encoding for the frame.

[0105] Mesh Simplification: The process of simplifying an input mesh to create a simplified mesh, called a base mesh. Vertices to be removed from the original mesh can be selected based on user-defined criteria, and the selected vertices and triangles connected to the selected vertices can then be removed.

[0106] In the process of performing mesh simplification, the voxelized input mesh, the target triangle ratio (TTR) and the minimum triangle component (CCCount) information can be transmitted as input, and a simplified mesh can be obtained as output. In this process, connected triangle components that are smaller than the set minimum triangle component (CCCount) can be removed.

[0107] UV parameterization: The process of mapping a 3D surface to the texture domain of a simplified mesh. Parameterization can be performed using the UVAtlas tool. This process generates mapping information that indicates where each vertex of the simplified mesh can be mapped to on the 2D image. The mapping information is represented as texture coordinates and stored, and the final base mesh is generated through this process.

[0108] Fitting subdivision surface (300): A process of performing subdivision on a simplified mesh (i.e., a simplified mesh with texture coordinates). The displacement and base mesh generated by the process are output to the encoder 201. A user-defined method (e.g., edge midpoint method) may be applied as a subdivision method. The fitting process is performed so that the input mesh and the subdivided mesh become similar to each other. The mesh on which the fitting process is performed will be referred to herein as a fitted subdivided mesh.

[0109] Figure 4 An edge midpoint subdivision method according to an embodiment is shown.

[0110] Figure 4 Show reference Figure 3 Describes the edge midpoint subdivision method for fitting subdivision surfaces. Figure 4 , the original mesh containing four vertices is subdivided to create sub-meshes. The sub-meshes can be created by creating new vertices in the middle of the edges between the vertices. Then, a fitting process is performed to make the input mesh and the sub-mesh similar to each other, resulting in a fitted subdivided mesh.

[0111] Once the fitted subdivision mesh is generated, the displacement is calculated based on the result and the previously compressed and decoded base mesh (hereinafter referred to as the reconstructed base mesh). In other words, the reconstructed base mesh is subdivided in the same way as the fitted subdivision surface. The position difference between the result and each vertex in the fitted subdivision mesh is the displacement of each vertex. Since the displacement represents the position difference in 3D space, it is expressed as a value in the (x, y, z) space in the Cartesian coordinate system. According to the user input parameters, the (x, y, z) coordinate value can be converted to the (normal, tangent, bitangent) coordinate value in the local coordinate system.

[0112] Figure 5 A displacement generation process according to an embodiment is shown. Figure 5 The displacement generation process may be performed by the preprocessor 200 , or may be performed by the encoder 201 .

[0113] Figure 5 Detailed description for reference Figure 4 The fitting of the subdivision surface 300 is described to calculate the displacement.

[0114] The encoder and / or preprocessor according to the embodiment may include 1) a subdivider, 2) a local coordinate system calculator and 3) a displacement vector calculator. The subdivider may perform subdivision on the reconstructed base mesh to generate a subdivided reconstructed base mesh. Here, the reconstruction of the base mesh may be performed by the preprocessor 200, or may be performed by the encoder 201. The local coordinate system calculator may receive a fitted subdivided mesh and a subdivided reconstructed base mesh, and may transform a coordinate system associated with the mesh into a local coordinate system based on the received mesh. The local coordinate system calculation may be optional. The displacement calculator calculates the position difference between the fitted subdivided mesh and the subdivided reconstructed base mesh. For example, it may generate the position difference between vertices in two input meshes. The position difference between the vertices is the displacement.

[0115] The mesh data transmission method and device according to the embodiment may encode the mesh data as follows. Mesh data is a term including point cloud data. Point cloud data (which may be simply referred to as point cloud) according to the embodiment may refer to data including vertex coordinates (also referred to as geometric information) and color information (also referred to as attribute information). In addition, geometric images, attribute images, occupancy maps, and auxiliary information (also referred to as patch information) generated by patch generation and packaging based on vertex coordinates and color information may also be referred to as point cloud data. Therefore, point cloud data including connection information may be referred to as mesh data. The terms point cloud and mesh data may be used interchangeably herein.

[0116] According to an embodiment, the V-Mesh compression (reconstruction) method may include intra-frame coding ( Figure 6 ) and inter-frame coding ( Figure 7 ).

[0117] Based on the results generated by the GoF, intra-frame coding or inter-frame coding is performed. In intra-frame coding, the data to be compressed can be base grids, displacements, attribute maps, etc. In inter-frame coding, the data to be compressed can be displacements, attribute maps, and the motion field between the reference base grid and the current base grid.

[0118] Figure 6 The intra-frame encoding process in the V-MESH compression method according to the embodiment is shown. Figure 6 The various components of the intra-frame encoding process correspond to hardware, software, processor and / or a combination thereof.

[0119] Figure 6 The encoding process is described in detail Figure 1 That is, it represents the encoding of the grid video encoder 102. Figure 1The encoding is the configuration of the grid video encoder 102 during intra-frame encoding. Figure 6 The encoder may include a pre-processor 200 and / or an encoder 201 . Figure 6 The preprocessor 200 and the encoder 201 may correspond to Figure 3 A preprocessor 200 and an encoder 201 are provided.

[0120] The preprocessor 200 may receive an input mesh and perform the above-mentioned preprocessing, and may generate a base mesh and / or a fitted subdivided mesh through the preprocessing.

[0121] The quantizer 411 of the encoder 201 may quantize the base grid and / or the fitted subdivided grid. The static grid encoder 412 may encode the static grid (i.e., the quantized base grid) and generate a bitstream containing the encoded base grid (i.e., a compressed base grid bitstream). The static grid decoder 413 may decode the encoded static grid (i.e., the encoded base grid). The inverse quantizer 414 may inverse quantize the quantized static grid (i.e., the base grid) and output a reconstructed (restored) base grid. The displacement calculator 415 may generate displacements based on the reconstructed static grid (i.e., the base grid) and the fitted subdivided grid. According to an embodiment, the displacement calculator 415 subdivides the reconstructed base grid and then calculates the displacement, i.e., the position difference of each vertex between the subdivided base grid and the fitted subdivided grid. In other words, when the fitted subdivided grid is similar to the original grid, the displacement is a displacement vector that is the position difference between the vertices in the two grids. The forward linear lifter 416 may perform a lifting transform on the input displacement to generate a lifting coefficient (also called a transform coefficient). The quantizer 417 may quantize the lifting coefficient. The image packer 418 may pack the image based on the quantized lifting coefficients. The video encoder 419 may encode the packed image. That is, the quantized lifting coefficients are packed into frames as 2D images by the image packer 418, compressed by the video encoder 419, and output as a displacement bitstream (i.e., a compressed displacement bitstream).

[0122] The video decoder 420 decodes the compressed displacement bitstream. The image unpacker 421 may perform unpacking on the decoded displacement frame to output quantization lifting coefficients. The inverse quantizer 422 may inverse quantize the quantization lifting coefficients. The inverse linear lifting unit 423 applies inverse lifting to the inverse quantization lifting coefficients to generate a reconstructed displacement. The mesh reconstructor 424 restores the reconstructed and deformed mesh based on the reconstructed displacement output from the inverse linear lifting unit 423 and the reconstructed base mesh (also referred to as the subdivided reconstructed base mesh) output from the inverse quantizer 414. The reconstructed and deformed mesh is referred to herein as a reconstructed deformed mesh.

[0123] The attribute transfer 425 receives an input mesh and / or an input attribute map and regenerates the attribute map based on the reconstructed deformed mesh. The attribute map refers to a texture map corresponding to the attribute information in the mesh data component. In the present disclosure, the terms attribute map and texture map are used interchangeably. The push-pull fill unit 426 can fill data into the attribute map based on a push-pull method. The color space converter 427 can convert the space of the color component of the attribute map. For example, the attribute map can be converted from an RGB color space to a YUV color space. The video encoder 428 can encode the attribute map to output a compressed attribute bitstream.

[0124] The multiplexer 430 may multiplex the compressed base grid bitstream, the compressed displacement bitstream, and the compressed attribute bitstream to generate a compressed bitstream.

[0125] exist Figure 6 In the embodiment, the displacement calculator 415 may be included in the preprocessor 200. In addition, at least one of the quantizer 411, the static grid encoder 412, the static grid decoder 413, or the inverse quantizer 414 may be included in the preprocessor 200.

[0126] like Figure 6 As described in , the intra-frame encoding method includes base mesh encoding (also referred to as static mesh encoding). That is, when intra-frame encoding is performed on the current input mesh frame, the base mesh generated during the preprocessing of the preprocessor 200 may be quantized by the quantizer 411 and then encoded by the static mesh encoder 412 using the static mesh compression technology. For example, in the V-Mesh compression method, the Draco technology is applied to encode the base mesh, and vertex position information, mapping information (texture coordinates), vertex connection information, etc. related to the base mesh are compressed.

[0127] Figure 6 The encoder in compresses the base grid, displacements, and attributes in the frame to generate a bitstream, while Figure 7 The encoder in compresses the motion, displacement, and attributes between the current frame and the reference frame to generate a bitstream.

[0128] Figure 7 The inter-frame encoding process in the V-MESH compression method according to the embodiment is shown. Figure 7 The various components of the inter-frame encoding process correspond to hardware, software, a processor and / or a combination thereof.

[0129] Figure 7 The encoding process is described in detail. Figure 1 That is, it means when Figure 1 The encoding is the configuration of the encoder during inter-frame coding. Figure 7 The encoder may include a pre-processor 200 and / or an encoder 201 . Figure 7The preprocessor 200 and the encoder 201 may correspond to Figure 3 A preprocessor 200 and an encoder 201 are provided.

[0130] For Figure 6 The encoding operation corresponds to Figure 7 Components of the encoding operation, refer to Figure 6 That is, Figure 7 The operations of the quantizer 511, displacement calculator 515, wavelet transformer 516, quantizer 517, image packer 518, video encoder 519, video decoder 520, image unpacker 521, inverse quantizer 522 and inverse wavelet transformer 523, grid reconstructor 524, attribute transfer 525, push-pull fill 526, color space converter 527, video encoder 528 and multiplexer 530 are the same as those described above. Figure 6 The operations of the quantizer 411, static grid encoder 412, static grid decoder 413 and inverse quantizer 414, displacement calculator 415, forward linear lifting unit 416, quantizer 417, image packer 418, video encoder 419, video decoder 420, image unpacker 421, inverse quantizer 422, inverse linear lifting unit 423 and grid reconstruction 424, attribute transfer 425, push-pull filling 426, color space converter 427, video encoder 428 and multiplexer 430 are the same or similar, so the ... linear lifting unit 423 and grid reconstruction 424, attribute transfer 425, push-pull filling 426, color space converter 427, video encoder 428 and multiplexer 430 are the same or similar, so the operations of the quantizer 411, static grid encoder 412, static grid decoder 413 and inverse linear lifting unit 423 and grid reconstruction 424, attribute transfer 425, push-pull filling 426, color space converter 427, video encoder 428 and multiplexer 4 Figure 7 A detailed description is not given here to avoid redundancy.

[0131] exist Figure 7 In the embodiment of the present invention, for inter-frame based coding, the motion encoder 512 can obtain and encode the motion vector between the reconstructed quantized reference base grid and the quantized current base grid, and output the compressed motion bitstream. The motion encoder 512 can be called a motion vector encoder. The base grid reconstructor 513 can reconstruct the base grid based on the reconstructed quantized reference base grid and the encoded motion vector. The reconstructed base grid is inverse quantized by the inverse quantizer 514 and output to the displacement calculator 515.

[0132] exist Figure 7 In the embodiment, the displacement calculator 515 may be included in the preprocessor 200. In addition, at least one of the quantizer 511, the motion encoder 512, the base grid reconstructor 513, or the inverse quantizer 514 may be included in the preprocessor 200.

[0133] As reference Figure 7As described, the inter-frame coding method may include motion field coding (also known as motion vector coding). When the reference mesh and the current input mesh have a one-to-one vertex correspondence and only the position information about the vertices differs between them, inter-frame coding may be performed. When inter-frame coding is performed, the base mesh may not be compressed. Instead, the difference between the vertices of the reference base mesh and the current base mesh, that is, the motion field (or motion vector), may be calculated and encoded. The reference base mesh is the result of quantizing the decoded base mesh data and is determined by the reference frame index determined in the GoF generation. The motion field may be encoded as is. Alternatively, the predicted motion field may be calculated by averaging the motion fields of the reconstructed vertices among the vertices connected to the current vertex, and the residual motion field may be encoded as the difference between the value of the predicted motion field and the value of the motion field of the current vertex. The value of the residual motion field may be encoded using entropy coding. In addition to the motion field coding in the inter-frame coding, the process of encoding the displacement and attribute map is the same as the structure of the intra-frame coding method except for the base mesh coding.

[0134] Figure 8 A lifting transformation process of displacement according to an embodiment is shown.

[0135] Fig. 9 A process of packing transform coefficients (also called lifting coefficients) into a 2D image according to an embodiment is shown.

[0136] Figure 8 and Fig. 9 Shown separately Figure 6 and Figure 7 The process of transforming displacement and packing transform coefficients during the encoding process.

[0137] The encoding method according to an embodiment includes displacement encoding.

[0138] After base mesh encoding and / or motion field encoding, a reconstructed base mesh may be generated by reconstruction and inverse quantization, and displacement may be calculated between the subdivision result of the reconstructed base mesh and the fitted subdivision mesh generated by fitting the subdivision surface (see Figure 6 415 or Figure 7 515 in ). A data transformation process (eg, wavelet transform) may be applied to the displacement information for efficient encoding (see Figure 6 416 or Figure 7 516 in the above table).

[0139] Figure 8 Shown by Figure 6 Forward linear lifting unit 416 or Figure 7The wavelet transformer 516 of FIG. 510 uses a lifting transform to transform the displacement information. For example, a lifting transform based on a linear wavelet may be performed. The transform coefficients generated by the transform process are quantized by the quantizer 417 (or 517) and then packaged into a 2D image by the image packager 418 (or 518), such as Fig. 9 As shown. The transform coefficients can be organized into blocks, one block for every 256 (=16×16) units. The individual blocks can be packed in z-scan order. The number of rows in a block is fixed to 16, but the number of columns in a block can be determined by the number of vertices in the subdivided base grid. Within a block, the transform coefficients can be sorted and packed by Morton code. For packed images, displacement video can be generated per GoF. The displacement video can be encoded by the video encoder 419 (or 519) using a conventional video compression codec.

[0140] Reference Figure 8 , the base mesh (original) may include vertices and edges of LoD0. The first subdivided mesh generated by splitting (or subdividing) the base mesh includes vertices generated by further splitting (or subdividing) the edges of the base mesh. The first subdivided mesh includes vertices of LoD0 and vertices of LoD1. LoD1 includes subdivided vertices and vertices from the base mesh (LoD0). The first subdivided mesh may be split (or subdivided) to generate a second subdivided mesh. The second subdivided mesh includes LoD2. LoD2 includes base mesh vertices (LoD0), LoD1 includes vertices further split (or subdivided) from LoD0, and LoD2 includes vertices further split (or subdivided) from LoD1. LoD is a level of detail indicating how detailed the mesh data content is. As the index of the level increases, the distance between vertices decreases and the level of detail increases. In other words, as the value of LoD decreases, the details of the mesh data content deteriorate. As the value of LoD decreases, the details of the mesh data content increase. LoD N includes the vertices included in LoD N-1. In the case where the mesh (or vertex) is further divided by subdivision, the mesh may be encoded based on a prediction and / or update method taking into account previous vertices v1 and v2 and subdivided vertex v. Instead of encoding the information of the current LoD N as is, a residual relative to the previous LoD N-1 may be generated. Therefore, the residual may be used to encode the mesh to reduce the size of the bitstream. The prediction process refers to the operation of predicting the current vertex v from previous vertices v1 and v2. Since adjacent subdivided meshes have similar data, this property may be utilized for efficient encoding. The current vertex position information is predicted from the residual of the previous vertex position information, and the previous vertex position information is updated by the residual. In the present disclosure, vertices and points may be used interchangeably. LoD may be defined in the subdivision of the base mesh. Depending on the embodiment, the subdivision of the base mesh may be performed by the preprocessor 200, or may be performed by a separate component / module.

[0141] Reference Fig. 9, the vertex has a transformation coefficient (also referred to as a lifting coefficient) generated by the lifting transformation. The transformation coefficient of the vertex related to the lifting transformation can be packed into the image by the image packer 418 (or 518) and then encoded by the video encoder 419 (or 519).

[0142] Fig.10 The attribute transfer process in the V-MESH compression method according to the embodiment is shown.

[0143] According to an embodiment, Fig.10 Show Figure 6 , Figure 7 Detailed operation of attribute transfer 425 (or 525) in the encoding of etc.

[0144] According to an embodiment, the encoding includes property graph encoding. According to an embodiment, the property graph encoding may be Figure 6 Video encoder 428 or Figure 7 The video encoder 528 executes.

[0145] According to an embodiment, in the present disclosure, the encoder compresses information about the input mesh through base mesh encoding (i.e., intra-frame encoding), motion field encoding (i.e., inter-frame encoding), and displacement encoding. The compressed input mesh in the encoding process is reconstructed through base mesh decoding (intra-frame), motion field decoding (inter-frame), and displacement video decoding, and as a result of the reconstruction, the reconstructed deformed mesh (hereinafter referred to as the reconstructed deformed mesh) is used to compress the input attribute map, such as Figure 6 and Figure 7 The reconstructed deformed mesh has position information about vertices, texture coordinates, and corresponding connectivity information, but no color information corresponding to the texture coordinates. Fig.10 As shown, in the V-Mesh compression method, a new attribute map having color information corresponding to the texture coordinates of the reconstructed deformed mesh is regenerated through the attribute transfer process of attribute transfer 425 (or 525).

[0146] According to an embodiment, attribute transfer 425 (or 525) first checks for each point P (u, v) in the 2D texture domain whether the corresponding vertex is within the texture triangle of the reconstructed deformed mesh. When the corresponding vertex is in the texture triangle T, the attribute transfer calculates the barycentric coordinates (α, β, γ) of P (u, v) according to the triangle T. Then, it calculates the 3D coordinates M (x, y, z) of P (u, v) based on the 3D vertex position and (α, β, γ) of the triangle T. The vertex coordinates M' (x', y', z') corresponding to the position closest to the calculated M (x, y, z) and the triangle T' containing the vertex are searched in the input mesh domain. Then, the barycentric coordinates (α', β', γ') of M' (x', y', z') in the triangle T' are calculated. The texture coordinates (u', v') are calculated based on the texture coordinates and (α', β', γ') corresponding to the three vertices of the triangle T', and the color information corresponding to the coordinates is searched in the input attribute map. The color information found in this manner is then assigned to the (u, v) pixel position in the new input attribute map. If P(u, v) does not belong to any triangle, a filling algorithm (e.g., the push-pull algorithm of push-pull filling 426 (or 526)) is used to fill the pixel at that position in the new input attribute map with the color value.

[0147] The new property graph generated by the property transfer 425 (or 525) is bundled into the GoF to construct a property graph video, which is compressed using the video codec of the video encoder 428 (or 528).

[0148] Available from Fig.10 See the reference relationship between the input mesh, input attribute map, reconstructed deformed mesh and reconstructed attribute map.

[0149] Figure 1 The decoding process can be performed Figure 1 Specifically, the decoding process is performed as disclosed below.

[0150] Fig.11 The intra-frame decoding process of the V-Mesh technology according to an embodiment is shown.

[0151] Fig.11 Show Figure 1 The configuration and operation of the grid video decoder 113 of the receiving device. In addition, Fig.11 It can be shown that by executing Figure 6 The mesh data is reconstructed by the inverse process of the intra-frame encoding process. Fig.11 The various components of the intra-frame decoding process correspond to hardware, software and / or a combination thereof.

[0152] First, the bitstream (i.e., compressed bitstream) received and input to the demultiplexer 611 of the intra decoder 610 may be separated into a mesh substream, a displacement substream, an attribute map substream, and a substream containing patch information about the mesh (e.g., V-PCC / V3C). The term V-PCC (video-based point cloud compression) used in the present disclosure may have the same meaning as V3C (visual volumetric video-based coding). The two terms may be used interchangeably. Therefore, in the present disclosure, the term V-PCC may be interpreted as V3C.

[0153] According to an embodiment, the grid substream may be input to and decoded by the static grid decoder 612 , the displacement substream may be input to and decoded by the video decoder 613 , and the property map substream may be input to and decoded by the video decoder 617 .

[0154] According to an embodiment, the mesh substream may be decoded by a decoder 612 of a static mesh codec (e.g., Google Draco) used in encoding to reconstruct connection information, vertex geometry information, vertex texture coordinates, etc. related to the decoding result of the reconstructed quantized base mesh (e.g., the reconstructed base mesh).

[0155] According to an embodiment, the displacement substream may be decoded into a displacement video by a decoder 613 of a video compression codec used in encoding. Then, image depacketization is performed by an image depacketizer 614, inverse quantization is performed by an inverse quantizer 615, and inverse transformation is performed by an inverse linear enhancement unit 616 to reconstruct displacement information about each vertex (i.e., reconstruct displacement).

[0156] According to an embodiment, the base grid reconstructed by the static grid decoder 612 is inversely quantized by the inverse quantizer 620 and output to the grid reconstructor 630. The grid reconstructor 630 reconstructs the reconstructed deformed grid (i.e., the decoded grid) based on the reconstructed displacement output from the inverse linear lifting unit 616 and the reconstructed base grid output from the inverse quantizer 620. In other words, the inversely quantized reconstructed base grid is combined with the reconstructed displacement information to generate a final decoded grid. In the present disclosure, the final decoded grid is referred to as a reconstructed deformed grid.

[0157] According to an embodiment, the property map substream is decoded by a decoder 617 corresponding to the video compression codec used in encoding, and then a color transformer 640 reconstructs a final property map (ie, a decoded property map) through color format conversion, color space conversion, etc.

[0158] According to an embodiment, the reconstructed decoded mesh and the decoded property map may be used as final mesh data available to a user at the receiving side.

[0159] Reference Fig.11, the received compressed bitstream includes patch information, a grid substream, a displacement substream and an attribute map substream. The term substream is interpreted to refer to a portion of a bitstream included in a bitstream. The bitstream contains patch information (data), grid information (data), displacement information (data) and attribute map information (data).

[0160] As mentioned above, Fig.11 The decoder performs intra-frame decoding as follows. The static grid decoder 612 decodes the grid substream to generate a reconstructed quantized base grid, and the inverse quantizer 620 inversely applies the quantization parameters of the quantizer to generate the reconstructed base grid. The video decoder 613 decodes the displacement substream, the image unpacker 614 unpacks the image of the decoded displacement video, and the inverse quantizer 615 inversely quantizes the quantized image. The inverse linear lifting unit 616 applies the lifting transform in the inverse process of the encoder to generate the reconstructed displacement. The grid reconstructor 630 generates a reconstructed deformed grid based on the reconstructed base grid and the reconstructed displacement. The video decoder 617 decodes the attribute map substream, and the color transformer 64 transforms the color format and / or space of the decoded attribute map to generate a decoded attribute map.

[0161] Fig.12 The inter-frame decoding process of the V-Mesh technology is shown.

[0162] Fig.12 Show Figure 1 Configuration and operation of the grid video decoder 113 of the receiving device. Fig.12 In the Figure 7 The mesh data is reconstructed by the inverse process of the inter-frame coding process. Fig.12 The various components of the intra-frame decoding process correspond to hardware, software and / or a combination thereof.

[0163] First, the bitstream received and input to the demultiplexer 711 of the intra decoder 710 can be separated into a motion substream (also called a motion vector substream), a displacement substream, a property map substream, and a substream containing patch information about the grid (e.g., V3C / V-PCC).

[0164] According to an embodiment, the motion substream may be input to and decoded by the motion decoder 712 , the displacement substream may be input to and decoded by the video decoder 713 , and the property map substream may be input to and decoded by the video decoder 717 .

[0165] According to an embodiment, the motion substream is decoded by the motion decoder 712 through entropy decoding and inverse prediction to reconstruct motion information (also called motion vector information). The base grid reconstructor 718 combines the reconstructed motion information with the pre-reconstructed and stored reference base grid to generate a reconstructed quantized base grid for the current frame. The inverse quantizer 720 applies inverse quantization to the reconstructed quantized base grid to generate a reconstructed base grid. The video decoder 713 decodes the displacement substream, the image unpacker 714 unpacks the image of the decoded displacement video, and the inverse quantizer 715 inverse quantizes the quantized image. The inverse linear lifting unit 716 applies the lifting transform in the inverse process of the encoder to generate a reconstructed displacement. The grid reconstructor 730 generates a reconstructed deformed grid (i.e., the final decoded grid) based on the reconstructed base grid and the reconstructed displacement.

[0166] According to an embodiment, the video decoder 717 decodes the attribute map substream in the same manner as intra-frame decoding, and the color converter 740 converts the color format and / or space of the decoded attribute map to generate a decoded attribute map. The decoded grid and the decoded attribute map can be used as final grid data available to the user at the receiving side.

[0167] Reference Fig.12 , the bitstream contains motion information (also called motion vectors), displacements, and attribute maps. Because inter-frame decoding is performed, Fig.12 The process also includes decoding inter-frame motion information. The reconstructed basic grid is generated by decoding the motion information and generating a reconstructed quantized basic grid for the motion information based on the reference basic grid. Fig.12 Zhongyu Fig.11 The same operation as in Fig.11 Description.

[0168] Fig.13 A mesh data transmitting device according to an embodiment is shown.

[0169] Fig.13 Corresponds to Figure 1 The transmitting device 100 or the grid video encoder 102, Figure 2 , Figure 6 or Figure 7 encoder (preprocessor and encoder) and / or corresponding sending encoding device. Fig.13 The various components correspond to hardware, software, processors and / or a combination thereof.

[0170] The operation process of using V-Mesh compression technology to compress and send dynamic mesh data at the sending end can be as follows: Fig.13 Configuration shown. Fig.13 The sending device can perform intra-frame coding (also known as intra-frame coding or intra-picture coding) and / or inter-frame coding (also known as inter-frame coding or inter-picture coding).

[0171] The preprocessor 811 receives the original mesh and generates a simplified mesh (or base mesh) and a fitting subdivision (or subdivision) mesh. Simplification can be performed based on a target number of vertices or a target number of polygons constituting the mesh. Parameterization can be performed on the simplified mesh to generate texture coordinates and texture connection information for each vertex. For example, parameterization is a process of mapping a 3D surface into a texture domain of a simplified mesh. When parameterization is performed using the UVAtlas tool, mapping information indicating where each vertex of the simplified mesh can be mapped on a 2D image is generated. The mapping information is represented as texture coordinates and stored, and the final base mesh is generated through this process. The mesh information can be quantized from a floating point form to a fixed point form. The result is a base mesh, which can be output to a motion vector encoder 813 or a static mesh encoder 814 through a switch unit 812. The preprocessor 811 can perform mesh subdivision on the base mesh to generate additional vertices. According to the subdivision method, vertex connection information including additional vertices, texture coordinates, and connection information about the texture coordinates can be generated. The preprocessor 811 can generate a fitting subdivision mesh by adjusting the vertex positions so that the subdivided mesh becomes similar to the original mesh.

[0172] According to an embodiment, when inter-coding is performed on a grid frame, the base grid is output to a motion vector encoder 813 through a switch unit 812. When intra-coding is performed on a grid frame, the base grid is output to a static grid encoder 814 through a switch unit 812. The motion vector encoder 813 may be referred to as a motion encoder.

[0173] For example, when intra-coding is performed on the mesh frame, the base mesh may be compressed by the static mesh encoder 814. In this case, connection information, vertex geometry information, vertex texture information, normal information, etc. related to the base mesh may be encoded. The base mesh bitstream generated by the encoding is sent to the multiplexer 823.

[0174] As another example, when inter-frame coding is performed on a grid frame, the motion vector encoder 813 may receive a base grid and a reference reconstructed base grid (or a reconstructed quantized reference base grid) as input, calculate a motion vector between the two grids, and encode its value. In addition, the motion vector encoder 813 may 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 by the encoding is sent to the multiplexer 823.

[0175] The base mesh reconstructor 815 may receive a base mesh encoded by the static mesh encoder 814 or a motion vector encoded by the motion vector encoder 813, and generate a reconstructed base mesh. For example, the base mesh reconstructor 815 may perform static mesh decoding on the base mesh encoded by the static mesh encoder 814 to reconstruct the base mesh. In this case, quantization may be applied before static mesh decoding, and inverse quantization may be applied after static mesh decoding. In another example, the base mesh reconstructor 815 may reconstruct the base mesh based on the reconstructed quantized reference base mesh and the motion vector encoded by the motion vector encoder 813. The reconstructed base mesh is output to the displacement calculator (or displacement vector calculator) 816 and the mesh reconstructor 820.

[0176] The displacement calculator 816 may perform mesh subdivision on the reconstructed base mesh. The displacement calculator 816 may calculate a displacement vector, which is a value of a vertex position difference between the subdivided reconstructed base mesh and the fitted subdivided (or subdivided) mesh generated by the preprocessor 811. In this case, as many displacement vectors as vertices in the subdivided mesh may be calculated. The displacement calculator 816 may transform the displacement vector calculated in the 3D Cartesian coordinate system to the local coordinate system based on the normal vector of each vertex.

[0177] The displacement vector video generator 817 may include a linear lifting part, a quantizer, and an image packer. That is, in the displacement vector video generator 817, the linear lifting unit may transform the displacement vector for efficient encoding. According to an embodiment, the transformation may be a lifting transformation, a wavelet transformation, etc. In addition, the quantizer may perform quantization on the transformed displacement vector value (i.e., the transform coefficient). In this case, different quantization parameters may be applied to the axes of the transform coefficients respectively. The quantization parameters may be derived by convention between the encoder / decoder. After transformation and quantization, the displacement vector information may be packed into a 2D image by the image packer. The displacement vector video generator 817 may generate a displacement vector video by grouping the packed 2D images of each frame. A displacement vector video may be generated for each group of frames (GoF) of an input grid.

[0178] The displacement vector video encoder 818 may encode the generated displacement vector video using a video compression codec. The generated displacement vector video bitstream is sent to a multiplexer 823.

[0179] The displacement vector reconstructor 819 may include a video decoder, an image unpacker, an inverse quantizer, and an inverse linear lifting part. That is, in the displacement vector reconstructor 819, the encoded displacement vector is decoded by the video decoder, the image unpacker performs image unpacking, the inverse quantizer performs inverse quantization, and the inverse linear lifting unit performs inverse transformation to reconstruct the displacement vector. The reconstructed displacement vector is output to the mesh reconstructor 820. The mesh reconstructor 820 reconstructs the deformed mesh based on the base mesh reconstructed by the base mesh reconstructor 815 and the displacement vector reconstructed by the displacement vector reconstructor 819. The reconstructed mesh (also referred to as the reconstructed deformed mesh) has reconstructed vertices, inter-vertex connection information, texture coordinates, and inter-texture coordinate connection information.

[0180] The texture map video generator 821 may regenerate the texture map based on the texture map (or attribute map) of the original mesh and the reconstructed deformed mesh output from the mesh reconstructor 820. According to an embodiment, the texture map video generator 821 may assign vertex-by-vertex color information in the texture map of the original mesh to the texture coordinates of the reconstructed deformed mesh. According to an embodiment, the texture map video generator 821 may generate a texture map video by grouping the texture maps regenerated at the frame level into GoFs.

[0181] The generated texture map video may be encoded by the texture map video encoder 822 using a video compression codec. The texture map video bitstream generated by the encoding is sent to the multiplexer 823.

[0182] The multiplexer 823 multiplexes the motion vector bitstream (for example, in the case of inter-frame coding), the base grid bitstream (for example, in the case of intra-frame coding), the displacement vector bitstream, and the texture map bitstream into a single bitstream. This single bitstream can be sent to the receiving side through the transmitter 824. Alternatively, for the motion vector bitstream, the base grid bitstream, the displacement vector bitstream, and the texture map bitstream, a file with one or more track data may be generated, or the bitstream may be encapsulated into fragments and sent to the receiving side through the transmitter 824.

[0183] Reference Fig.13, the transmitter (encoder) can encode the mesh in an intra-frame or inter-frame manner. According to intra-frame coding, the transmitting device can generate a base mesh, a displacement vector (or displacement) and a texture map (or attribute map). According to inter-frame coding, the transmitting device can generate a motion vector (or motion), a displacement vector (or displacement) and a texture map (or attribute map). The texture map obtained from the data input unit is generated and encoded based on the reconstructed mesh. The displacement is generated and encoded based on the vertex position difference between the base mesh and the segmented (or subdivided) mesh. More specifically, the displacement is the position difference between the fitted subdivided mesh and the subdivided reconstructed base mesh, that is, the vertex position difference between the two meshes. The base mesh is generated by simplifying the original mesh through preprocessing and encoding the simplified mesh. For motion, a motion vector is generated for the mesh of the current frame based on the reference base mesh in the previous frame.

[0184] Fig.14 A mesh data receiving device according to an embodiment is shown.

[0185] Fig.14 Corresponds to Figure 1 The receiving device 110 or the grid video decoder 113, Fig.11 or Fig.12 decoder and / or corresponding receiving decoding device. Fig.14 The various components correspond to hardware, software, processors and / or a combination thereof. Fig.14 The receiving (decoding) operation can be followed Fig.13 The reverse process of the corresponding process of the sending (encoding) operation.

[0186] The bit stream of the mesh data received by the receiver 910 is subjected to file / segment decapsulation and then demultiplexed into a compressed motion vector bit stream (e.g., inter-frame decoding) or a base mesh bit stream (e.g., intra-frame decoding), a displacement vector bit stream, and a texture map bit stream by the demultiplexer 911. For example, when the current mesh is inter-frame encoded, the motion vector bit stream is received, demultiplexed, and then output to the motion vector decoder 913 through the switch unit 912. In another example, when the current mesh is intra-frame encoded, the base mesh bit stream is received, demultiplexed, and then output to the static mesh decoder 914 through the switch unit 912. Here, the motion vector decoder 913 may be referred to as a motion decoder.

[0187] According to an embodiment, in the case where inter-frame coding is applied to the current grid based on the frame header information, the motion vector decoder 913 may decode the motion vector bitstream. According to an embodiment, the motion vector decoder 913 may use the previously decoded motion vector as a predictor and add it to the residual motion vector decoded from the bitstream to reconstruct the final motion vector.

[0188] According to an embodiment, when intra-coding is applied to the current mesh based on frame header information, the static mesh decoder 914 may decode the base mesh bitstream to reconstruct connection information, vertex geometry information, texture coordinates, normal information, etc. related to the base mesh.

[0189] According to an embodiment, the base grid reconstructor 915 may reconstruct the current base grid based on the decoded motion vector or the decoded base grid. For example, in the case where inter-frame coding is applied to the current grid, the base grid reconstructor 915 may add the decoded motion vector to the reference base grid and perform inverse quantization to generate a reconstructed base grid. In another example, in the case where intra-frame coding is applied to the current grid, the base grid reconstructor 915 may perform inverse quantization on the base grid decoded by the static grid decoder 914 to generate a reconstructed base grid.

[0190] According to an embodiment, the displacement vector video decoder 917 may decode the displacement vector bitstream into a video bitstream using a video codec.

[0191] According to an embodiment, the displacement vector reconstructor 918 extracts displacement vector transform coefficients from the decoded displacement vector video, and applies inverse quantization and inverse transform to the extracted displacement vector transform coefficients to reconstruct the displacement vector. To this end, the displacement vector reconstructor 918 may include an image unpacker, an inverse quantizer, and an inverse linear lifting section. If the reconstructed displacement vector is a value in a local coordinate system, an inverse transform to a Cartesian coordinate system may be performed.

[0192] The mesh reconstructor 916 may subdivide the reconstructed base mesh to generate additional vertices. By subdividing, vertex connection information including additional vertices, texture coordinates, and connection information about the texture coordinates may be generated. In this case, the mesh reconstructor 916 may combine the subdivided reconstructed base mesh with the reconstructed displacement vectors to generate a final reconstructed mesh (also referred to as a reconstructed deformed mesh).

[0193] According to an embodiment, the texture map video decoder 919 may decode the texture map bitstream into a video bitstream using a video codec to reconstruct the texture map. The reconstructed texture map has color information about each vertex in the reconstructed mesh, and the texture coordinates of each vertex can be used to obtain the color value of the vertex from the texture map.

[0194] According to an embodiment, the mesh reconstructed from the mesh reconstructor 916 and the texture map reconstructed from the texture map video decoder 919 are presented to the user through a rendering process in the mesh data renderer 920 .

[0195] Reference Fig.14, the receiving device (decoder) may decode the mesh in an intra-frame or inter-frame manner. According to intra-frame decoding, the receiving device may receive the base mesh, the displacement vector (or displacement), and the texture map (or attribute map), and render the mesh data based on the reconstructed mesh and the reconstructed texture map. According to inter-frame decoding, the receiving device may receive the motion vector (or motion), the displacement vector (or displacement), the texture map (or attribute map), and render the mesh data based on the reconstructed mesh and the reconstructed texture map.

[0196] The mesh data sending device and method according to the embodiment may preprocess the mesh data, encode the preprocessed mesh data, and send a bit stream containing the encoded mesh data. The point mesh data receiving device and method according to the embodiment may receive a bit stream containing mesh data and decode the mesh data. The mesh data sending / receiving method / device according to the embodiment may be abbreviated as the method / apparatus according to the embodiment. The mesh data sending / receiving method / device according to the embodiment may also be referred to as the 3D data sending / receiving method / device according to the embodiment.

[0197] As mentioned above, the sending device first Figure 6 , Figure 7 or Fig.13 The preprocessing is performed on the input raw grid as shown. More specifically, Figure 3 As shown, the mesh simplification unit of the preprocessor 200 generates a simplified mesh of the input original mesh, and the atlas parameterization (also called UV parameterization) unit generates texture coordinates of the vertices constituting the simplified mesh. Then, the simplified mesh and the texture coordinates are compressed and reconstructed into the basic mesh data of the input original mesh.

[0198] at this time, Figure 6 Attribute transfer 425, Figure 7 Property transfer 525 or Fig.13 The texture map video generator 821 regenerates a new texture map based on the texture map of the original mesh and the texture coordinates of the encoded reconstructed mesh. Here, the reconstructed mesh has the result of performing subdivision on the reconstructed base mesh and has texture coordinates of values ​​calculated based on the texture coordinates generated by the preprocessor 200. The texture map image regenerated based on the texture coordinates of the reconstructed mesh is processed into a video and is decoded by an existing video codec (e.g., Figure 6 Video encoder 428, Figure 7 Video encoder 528 or Fig.13 Thus, the texture coordinates generated by the preprocessor 200 will affect the structure / shape of the reconstructed texture image, and then will affect the performance of the texture video compression.

[0199] Fig.15An example of a texture map video regenerated according to the above V-Mesh method is shown. Specifically, when the texture coordinates of the simplified mesh are generated in the atlas parameterization of the preprocessor 200, the texture coordinates of each vertex are generated based only on the information about the current frame. Then, when the base mesh with the generated texture coordinates is compressed and reconstructed and used for texture map regeneration, the texture coordinates of the base mesh are regenerated by attribute transfer (see Figure 6 425 or Figure 7 525) or Fig.13 The texture map regenerated by the texture map video generator 821 has low image correlation between frames, such as Fig.15 For example, in Fig.15 In , the mesh patch of the face may be located near the lower right corner in frame i (951), near the center left in frame i+1 (952), split into two parts near the center right in frame i+2 (953, 954), and near the upper right corner in frame i+3 (955). Therefore, in the parameterized operation, the texture map regenerated based on the texture coordinates of the simplified mesh generated based only on the current frame information and the original texture map has low image correlation between frames and little temporal consistency.

[0200] In particular, if Figure 7 or Fig.13 When compressing a texture map video using a video codec as shown, that is, when applying inter-frame coding to compress the texture map video, a large amount of residual signal data to be encoded may be generated due to the low accuracy of inter-frame prediction, and therefore many compressed bit streams may be generated. In addition, a larger encoding bit stream size of the input grid may require more resources and costs for system operations such as data transmission and storage.

[0201] In other words, in the V-Mesh compression method described so far, the input dynamic mesh data is simplified, and the simplified mesh data is encoded using a static mesh compression method. The simplified mesh data includes geometric information about the vertices that make up the mesh and texture coordinate information for retrieving color information about each vertex from a texture map. V-Mesh processes the texture coordinates of the original mesh to generate texture coordinates of the simplified mesh. The generated texture coordinates are then processed to be used more efficiently to compress the texture map video than the texture coordinates of the original mesh. However, since they do not reflect the temporal coherence of the video, there are limitations in achieving sufficient performance and efficiency when applying an inter-frame compression method for compression. In particular, as the input mesh content and its texture map resolution increase and the target bit rate increases, the resolution and capacity of the compressed texture map video increase. Therefore, there may be limitations in compressing, sending, and utilizing mesh content using the above method.

[0202] Therefore, in order to improve the compression performance of texture map video using a video codec, a method for generating new texture coordinates is proposed so that temporal consistency can be reflected as much as possible in the reconstructed texture map video stream. In other words, by using the method proposed in this article when a sending device encodes a texture map video, the compression performance of the texture map video can be improved. As a result, the compression performance of the dynamic mesh can be improved. In addition, fewer resources can be used when storing, utilizing and transmitting a bitstream generated after compressing mesh data obtained using an encoder applied in the present disclosure, and when storing and utilizing the bitstream on the receiving side. In other words, by regenerating and compressing a texture map (i.e., an attribute map) based on the method proposed in the present disclosure, the cost required to use mesh content in media and communication systems, etc. can be reduced, and the scope of applications utilizing the mesh content can be further expanded.

[0203] In other words, since the bitstream of the texture map video accounts for a large proportion of the mesh bitstream compressed by V-Mesh, using the method proposed in the present disclosure to improve the compression performance of the texture map video can improve the compression performance of V-Mesh.

[0204] Fig.16 is an example detailed block diagram of a parameterization unit according to an embodiment.

[0205] According to an embodiment, the parameterization unit comprises Figure 2 , Figure 3 , Figure 6 , Figure 7 or Fig.13 In the preprocessor 200. That is, Fig.16 The parameterization unit is located between the mesh simplification unit and the fitting subdivision surface unit in the pre-processor 200.

[0206] Fig.16 The parameterization unit may include a polygon / vertex segmentation unit 11011 , a mesh patch segmentation unit 11013 and a mesh patch packing unit 11015 . Fig.16 The various components used for parameterization may correspond to hardware, software, a processor and / or a combination thereof.

[0207] Fig.17 is a flow chart illustrating an example parameterization method according to an embodiment. In one embodiment, Fig.17 Operation 12011 by Fig.16 The polygon / vertex segmentation unit 11011 performs operation 12013 by Fig.16 The mesh patch segmentation unit 11013 is performed. In addition, operation 12015 is performed by Fig.16 The grid patch packing unit 11015 executes.

[0208] Will refer to Fig.16and Fig.17 Describes the parameterization process for generating texture coordinates for a simplified mesh.

[0209] First, the simplified mesh from the mesh simplification unit of the pre-processor 200 is input to the polygon / vertex segmentation unit 11011 of the parameterization part.

[0210] According to an embodiment, the polygon / vertex segmentation unit 11011 performs polygon or vertex segmentation (operation 12011) on the simplified mesh based on the characteristics of the polygons (triangles or rectangles) or vertices constituting the mesh. The segmentation in operation 12011 includes determining which direction of the plane of the bounding box enclosing the mesh object is most similar to the orientation of the polygon formed by the connection of the vertices constituting the mesh or the orientation of each vertex. In this case, the orientation can be determined by the normal vector of the polygon or the normal vector of the vertex. That is, the normal vector of the mesh polygon or the normal vector of the vertex is compared with the normal vectors of the six planes of the bounding box to determine the similarity, and the orientation of the plane with the most similar normal vector is determined for the polygon or vertex. According to an embodiment, the normal vector of the polygon can be calculated using the position coordinates of the vertices constituting the polygon. According to an embodiment, regarding the normal vector of the vertex, when the input mesh data contains vertex-specific normal information, the value of the information can be used. When the data does not contain normal information, the value can be calculated based on the vertex and its neighbors. To this end, the polygon / vertex segmentation unit 11011 can apply a method for calculating the normal of each point when generating a patch for a point cloud in V-PCC. The orientation of a polygon or vertex may be that of one of the six planes of the bounding box, or may be one of an orientation including additional orientations defined by the user, if any.

[0211] According to an embodiment, based on the direction (or orientation) information of the polygons or vertices obtained from the polygon / vertex segmentation unit 11011, the mesh patch segmentation unit 11013 performs a process of segmenting the segmented polygons or vertices into mesh patches, which are a set of adjacent (or neighboring) polygons having the same direction (operation 12013). In operation 12013, when mesh patch segmentation is performed based on polygons, polygons that are oriented in the same direction based on the current polygon and are adjacent to each other are calculated, and the maximum number of adjacent polygons (that is, the maximum number of polygons that can constitute a mesh patch) can be defined by the user. When mesh patch segmentation is performed based on polygons in operation 12013, the mesh patch segmentation unit 11013 can perform mesh patch segmentation on all polygons, and then include any polygons not included in the patch, whether in a patch in the most dominant orientation among the orientations of adjacent polygon patches, or in a polygon patch in the most similar orientation. When mesh patch segmentation is performed based on vertices in operation 12013 , the mesh patch segmentation unit 11013 may apply a method of segmenting a point cloud into patches when generating patches for the point cloud in the V-PCC.

[0212] According to the implementation mode, Fig.19 As shown, the mesh patch packing unit 11015 maps the mesh patches generated by the mesh patch segmentation unit 11013 onto a single 2D image. According to an embodiment, the mesh patch packing unit 11015 may perform the mesh patch packing by applying a point cloud patch packing method of V-PCC.

[0213] According to an embodiment, the mesh patch packing unit 11015 may refer to the packing result of the previous frame when mapping the generated mesh patch to a 2D image to output a simplified mesh with texture coordinates (operation 12015). That is, the mesh patch patching unit 11015 maps the generated mesh patch to the 2D image with reference to the packing result of the previous frame to generate mapping information for identifying where each vertex of the simplified mesh is mapped to on the 2D image. The mapping information is represented as texture coordinates to be stored.

[0214] In other words, the grid patch packing unit 11015 may perform grid patch packing by mapping the generated grid patches onto the 2D image in descending order of patch size. According to an embodiment, in order to ensure that each grid patch is mapped onto a 2D image of a size specified by a user, the grid patch packing unit 11015 may search for positions in a raster scan order starting from coordinates (0,0) of the image. In addition, the grid patch may be rotated by an angle specified by a user and mapped onto the 2D image (i.e., 2D frame). According to an embodiment, a new patch is not allowed to be mapped onto a position in the 2D image (i.e., 2D frame) that has been mapped and filled with a previous patch.

[0215] Fig.18 is a detailed flow chart showing an example mesh patch packing method used in a parameterization operation according to an embodiment. That is, Fig.18 is a flowchart illustrating an example method of mapping mesh patches with reference to packing results from a previous frame when the mesh patch packing unit 11015 performs packing to map mesh patches onto a single 2D image.

[0216] That is, in order to consider similarities between frames when mapping mesh patches onto a single 2D image, the mesh patch packing unit 11015 may pack mesh patches with reference to packing results from previous frames to generate texture coordinates.

[0217] First, it is checked whether there is a frame for which mesh patch packing has been previously completed (operation 13011).

[0218] When it is determined in operation 13011 that there is no frame for which grid patch packing has been previously completed, grid patch packing may be performed by mapping the generated grid patches onto the 2D image in descending order of the size of the generated grid patches as described above (operation 13012). According to an embodiment, in order to ensure that each grid patch is mapped onto a 2D image of a size specified by a user, a position may be searched in a raster scan order starting from coordinates (0,0) of the image. In addition, the grid patch may be rotated by an angle specified by a user and mapped onto the 2D image (i.e., 2D frame). In this case, a new patch is not allowed to be mapped onto a position in the 2D image (i.e., 2D frame) that has been mapped and filled with a previous patch.

[0219] When it is determined in operation 13011 that there is a frame in which mesh patch packing has been previously completed, it is determined whether there is a matching mesh patch among the mesh patches in the previous frame for each mesh patch in the current frame (operation 13013). The matching criteria in operation 13013 may include the orientation of the mesh patches and the position similarity of the polygons / vertices constituting the mesh patches. According to an embodiment, in operation 13013, when the orientations of the mesh patches are the same, the number of polygons / vertices constituting the mesh patches is similar, and their positions in 3D space or 2D space are similar, it may be determined that the two mesh patches match each other. For example, when at least one mesh patch in the previous frame is in the same orientation as the current mesh patch in the current frame and has a similar number of polygons / vertices and similar positions in 3D space or 2D space, it may be determined that the two mesh patches (i.e., at least one mesh patch in the previous frame and the current mesh patch in the current frame) match each other.

[0220] When it is determined in operation 13013 that there is no matching mesh patch in the previous frame for the current mesh patch in the current frame, the current mesh patch is mapped to a corresponding position on the current 2D image in a predetermined order as described above (operation 13015).

[0221] When it is determined in operation 13013 that there is a matching grid patch in the previous frame for the current grid patch, the current grid patch may be mapped to be located on the current 2D image with reference to the position on the 2D image to which the matching grid patch in the previous frame is mapped (operation 13014). For example, the current grid patch may be mapped to the current 2D image to have the same position as the matching grid patch in the previous frame. In the case where the same position on the current 2D image is occupied by another grid patch, the current grid patch may be mapped to the position closest to the occupied position. In some embodiments, the grid patches in the current frame for which matching grid patches have been found in the previous frame may be first mapped to the current 2D image, and then the unmatched grid patches may be mapped to appropriate positions in the remaining space of the 2D image. Through this process, the grid patches in the current frame may be mapped to positions similar to the grid patches in the previous frame.

[0222] Once the mesh patch packing is completed for the current frame by repeating the above process (operation 13016), the result is as follows: Fig.19 As shown on the right side of , the mesh patches constituting the simplified mesh can be located on the 2D image to which they are mapped. Then, the mapping positions of the vertices constituting each mesh patch on the 2D image can be obtained. The mapping positions of the vertices on the 2D image have 2D coordinate values. In the present disclosure, these coordinate values ​​are used as texture coordinates of the vertices. The texture coordinates are included in the simplified mesh as texture coordinates of each vertex and are compressed into information constituting the base mesh. That is, the simplified mesh with texture coordinates is input to the fitting subdivision surface part that performs subdivision (i.e., segmentation) and fitting processes. Then, the fitting subdivision mesh and the base mesh are output to the encoder 201. The operating details of the fitting subdivision surface part in this article refer to Figure 3 The description is omitted in this article to avoid redundancy.

[0223] Fig.19 An example of mapping a mesh patch constituting a simplified mesh mapped onto a 2D image is shown according to an embodiment.

[0224] According to an embodiment, the encoder 201 calculates displacement information (or displacement or displacement vector) based on the base mesh and the fitted subdivided mesh output by the preprocessor 200, and generates a reconstructed deformed mesh based on the calculated displacement information. For example, the reconstructed deformed mesh is obtained by adding the reconstructed displacement to the subdivided reconstructed base mesh. For details on generating the reconstructed deformed mesh, refer to Figure 6 , Figure 7 or Fig.13 The description is omitted in this article to avoid redundancy.

[0225] According to an embodiment, Figure 6 Attribute transfer 425, Figure 7 Property transfer 525 or Fig.13 The texture map video generator 821 regenerates the texture map (or attribute map) based on the texture map of the original mesh and the reconstructed deformed mesh as described above.

[0226] That is, execute the reference Figures 16 to 18 The process described enables the texture coordinates output by the parameterization unit of the pre-processor 200 to be used as the basis for determining where the color information about each vertex is stored in the 2D texture map when regenerating the texture map of the reconstructed mesh during the attribute transfer phase.

[0227] As described above, the present disclosure ensures that similar mesh patches from different frames are packed in similar locations on the 2D image through the above process. Therefore, similar mesh patches may have similar texture coordinates. As a result, the texture map regenerated based on the texture coordinates may have similar shapes across frames. Therefore, if Fig. 20 As shown, the finally generated texture map video can maintain temporal consistency as much as possible and can result in high compression performance when inter-frame prediction is applied to compress the texture map video.

[0228] Fig. 20 Another example of reconstructing a texture map video according to an embodiment is shown. That is, Fig. 20 An example of the result of mapping the mesh patches of the current frame onto a single 2D image with reference to the packing results of the previous frame is shown.

[0229] That is, when the texture coordinates of the simplified mesh are generated in the atlas parameterization operation of the preprocessor 200, the texture coordinates of each vertex are generated based on the packing result of the previous frame and the information about the current frame. Then, the base mesh with the generated texture coordinates is compressed and reconstructed. When used for texture map regeneration, such as Fig. 20 As shown, through attribute transfer (see Figure 6 425 or Figure 7 525) or Fig.13 The texture map regenerated by the texture map video generator 821 has high image correlation between frames. Fig.16 , in frame i, frame i+1, frame i+2, and frame i+3, mesh patches of the face may be packed at approximately the same position (i.e., near the lower right corner of the frame) 14051 to 14054. Therefore, in the parameterized operation, the texture map regenerated according to the texture coordinates of the simplified mesh generated based on the previous frame information and the current frame information and the original texture map has high image correlation between frames and maintains temporal consistency.

[0230] By property transfer (see Figure 6 425 or Figure 7 525) or Fig.13 The texture map video generator 821 regenerates the texture map by the video encoder (see Figure 6 428 of Figure 7 528 or Fig.13 822 in the example above) and output as a compressed attribute map bitstream. In the present disclosure, the attribute map bitstream and the compressed texture map bitstream can be used interchangeably. The compressed attribute bitstream is then multiplexed with other bitstreams by a multiplexer. It can then be sent to Fig.11 , Fig.12 or Fig.14 or can be encapsulated in files or fragments and sent to Fig.11 , Fig.12 or Fig.14 receiving device.

[0231] The above describes in detail the process of processing the compressed bitstream or file / fragment received from the sending device to reconstruct the mesh and attribute map. Fig.11 , Fig.12 or Fig.14 The receiving device will not be described below to avoid redundancy.

[0232] The 3D data transmitting apparatus and method described so far can be summarized as follows.

[0233] 1) For a simplified mesh, segmentation is performed by combining polygons or vertices having similar characteristics based on the characteristics of the polygons or vertices constituting the mesh.

[0234] 2) A collection of segmented polygons or vertices is formed into a mesh patch, and a mesh patch packing process is performed to map the mesh patch generated from the input frame onto a 2D image.

[0235] 3) Grid patch packing method A method of packing grid patches of a current frame by referring to packing results of a previous frame is applied so that inter-frame packing similarity can be considered.

[0236] 4) When all mesh patches are packed onto the 2D image, the mapped coordinate locations are used as texture coordinates for the individual vertices that make up the patch.

[0237] 5) The texture map regenerated based on the texture coordinates obtained above can have similar shapes across frames. The final texture map video generated based on the regenerated map can maintain temporal consistency as much as possible, thereby showing high compression performance in video compression based on inter-frame prediction.

[0238] Fig.21 is a flow chart showing an example transmission method according to an embodiment. The transmission method according to an embodiment may include: encoding mesh data (21011); and transmitting a bit stream including the encoded mesh data (21012).

[0239] According to an embodiment, the operation 21011 of encoding the mesh data may further include preprocessing the mesh data before encoding the mesh data. Figure 3 The preprocessor 200 executes. Figure 6 , Figure 7 or Fig.13 Shown including Figure 3 An example sending device of the pre-processor 200 is shown.

[0240] Depending on the implementation, preprocessing may include mesh simplification, parameterization, and fitting subdivision surface operations. Preprocessing may also include GoF generation. For details of each of these operations, refer to the above Figure 3 Description.

[0241] Depending on the implementation, parameterization may include polygon segmentation, mesh patch segmentation, and mesh patch packing. For details of each of these operations, refer to the above Figures 16 to 20 Description.

[0242] That is, as referenced Figures 16 to 20 As described, when polygon segmentation, mesh patch segmentation and mesh patch packing are performed, texture coordinates of the vertices of the simplified mesh are generated. The texture coordinates of the vertices of the simplified mesh are then included and encoded as base mesh data. The encoded base mesh is reconstructed by a base mesh reconstructor. The mesh reconstructor combines the reconstructed base mesh and the reconstructed displacement vectors to generate a reconstructed mesh. In other words, the reconstructed base mesh is subdivided and combined with the displacement vectors by the base mesh reconstructor, and the texture coordinates of the vertices additionally generated during the subdivision of the base mesh are calculated based on the texture coordinates of the reconstructed base mesh. As a result, the texture coordinates of the mesh reconstructed by the mesh reconstructor include the texture coordinates of the reconstructed base mesh and the texture coordinates of the subdivided vertices calculated based on this.

[0243] The texture map video generator (or attribute transfer) processes the original texture map to regenerate the texture map of the reconstructed mesh. In this operation, the vertices in the original mesh that are most similar to the vertices in the reconstructed mesh are found, and the color information about the vertices is obtained from the original texture map and assigned to the 2D image of the texture map to be regenerated. The texture coordinates of the vertices in the reconstructed mesh are the locations where the color information is assigned. In other words, a new texture map is regenerated based on the texture coordinates of the reconstructed mesh. The regenerated frame-specific texture map is processed as a video and compressed and sent by the texture map video encoder. The texture map video generator (or attribute transfer) can be referred to as the texture map video generation stage or the attribute transfer stage.

[0244] The texture coordinates generated in the preprocessing operation reflect inter-frame similarity, so the inter-frame similarity can be maintained in the texture map video regenerated by the texture map video generator (or attribute transfer), thereby further improving the compression performance when encoding the texture map video according to inter-frame coding.

[0245] Fig. 22 is a flowchart illustrating an example receiving method according to an embodiment. The receiving method according to an embodiment may include: receiving a bit stream containing mesh data (22011); and decoding the mesh data contained in the bit stream (22012).

[0246] For details of operation 22011 of receiving a bitstream containing mesh data and operation 22012 of decoding the mesh data contained in the bitstream, refer to Fig.11 , Fig.12 or Fig.14 The detailed description of the receiving device in will not be described again in this article to avoid redundancy.

[0247] Therefore, according to the present disclosure, the grid patch can be mapped to the 2D image with reference to the grid patch packing result in the previous frame, thereby reflecting the temporal consistency of the video. In other words, by segmenting the simplified grid into grid patches and mapping the patches to the 2D image with reference to the grid patch packing result in the previous frame, similar grid patches can be mapped to similar positions. Thus, the texture coordinates regenerated based on the mapping position can maintain the similarity between frames. As a result, the texture map image regenerated based on the texture coordinates can have similar structures and shapes across frames. In addition, when compressing images using a video codec, inter-frame prediction can be effectively applied, resulting in improved compression performance.

[0248] Therefore, the compression performance of texture map video can be improved, which in turn can lead to improved compression performance of mesh content using V-Mesh. As described above, the video bitstream is a very large part of the encoded mesh bitstream. Therefore, by reducing the resource share required by the grid system and reducing its usage cost, the grid system can operate more efficiently and the scope of applications utilizing the grid can be expanded. In particular, when users create and generate mesh content and transfer it for utilization, the mesh patch packing method that reflects the mesh patch packing results in the previous frame is more valuable. For example, a system / platform / service such as an AR / hologram-based video conferencing system that uses a 3D object reflecting the user's appearance for real-time communication can be an example. Therefore, the present disclosure can enhance the usability of V-Mesh.

[0249] As described above, according to the present disclosure, by considering the image similarity between frames when generating the texture coordinates of the simplified mesh, a texture map with high image correlation (i.e., maximum temporal consistency) between frames can be regenerated. This can improve the compression performance of the V-Mesh dynamic mesh, especially the compression performance of the texture map video of the mesh.

[0250] The above-mentioned various parts, modules or units can be software, processors or hardware parts that execute the continuous process stored in the memory (or storage unit). The various steps described in the above-mentioned embodiments can be performed by a processor, software or hardware part. The various modules / blocks / units described in the above-mentioned embodiments can be operated as a processor, software or hardware. In addition, the method presented in the embodiment can be executed as a code. The code can be written on a processor-readable storage medium, so it is read by a processor provided by the device.

[0251] In this specification, when a part "includes" or "contains" an element, unless otherwise mentioned, it means that the part also includes or contains another element. In addition, the term "...module (or unit)" disclosed in this specification means a unit for processing at least one function or operation, and can be implemented by hardware, software, or a combination of hardware and software.

[0252] Although the embodiments have been described with reference to the accompanying drawings for simplicity, new embodiments may be designed by combining the embodiments shown in the accompanying drawings. If a person skilled in the art designs a computer-readable recording medium having a program for executing the embodiments mentioned in the above description, it may fall within the scope of the attached claims and their equivalents.

[0253] The apparatus and method may not be limited to the configuration and method of the above-described embodiments. The above-described embodiments may be configured by selectively combining with each other entirely or partially, so that various modifications can be made.

[0254] Although preferred embodiments of the embodiments have been shown and described, the embodiments are not limited to the specific embodiments described above, and various modifications may be made by a person skilled in the art without departing from the spirit of the embodiments claimed for protection in the claims, and these modifications should not be understood in isolation from the technical ideas or vision of the embodiments.

[0255] Various elements of the device of the embodiment can be implemented by hardware, software, firmware or a combination thereof. Various elements in the embodiment can be implemented by a single chip (e.g., a single hardware circuit). According to the embodiment, the components according to the embodiment can be implemented as separate chips respectively. According to the embodiment, at least one or more components of the device according to the embodiment may include one or more processors capable of executing one or more programs. The one or more programs may execute any one or more of the operations / methods according to the embodiment, or include instructions for executing them. The executable instructions for executing the method / operation of the device according to the embodiment may be stored in a non-transitory CRM or other computer program products configured to be executed by one or more processors, or may be stored in a temporary CRM or other computer program products configured to be executed by one or more processors. In addition, the memory according to the embodiment can be used as a concept that not only covers volatile memory (e.g., RAM) but also covers non-volatile memory, flash memory and PROM. In addition, it can also be implemented in the form of a carrier wave (e.g., transmission via the Internet). In addition, the processor-readable recording medium can be distributed in a computer system connected via a network so that the processor-readable code can be stored and executed in a distributed manner.

[0256] In this document, the terms " / " and "," should be interpreted as indicating "and / or". For example, the expression "A / B" may mean "A and / or B". In addition, "A, B" may mean "A and / or B". In addition, "A / B / C" may mean "at least one of A, B, and / or C". "A / B / C" may mean "at least one of A, B, and / or C". In addition, in this document, the term "or" should be interpreted as indicating "and / or". For example, the expression "A or B" may include 1) only A, 2) only B, and / or 3) both A and B. In other words, the term "or" in this document should be interpreted as indicating "in addition or alternatively".

[0257] The various elements of the embodiments may be implemented by hardware, software, firmware or a combination thereof. The various elements of the embodiments may be performed by a single chip (e.g., a single hardware circuit). Depending on the embodiment, the elements may be selectively performed by separate chips, respectively. Depending on the embodiment, at least one element of the embodiments may be performed in one or more processors including instructions for performing operations according to the embodiments.

[0258] The operation according to the embodiment described in this specification may be performed by a sending / receiving device including one or more memories and / or one or more processors according to the embodiment. One or more memories may store programs for processing / controlling the operation according to the embodiment, and one or more processors may control the various operations described in this specification. One or more processors may be referred to as controllers, etc. In an embodiment, the operation may be performed by firmware, software, and / or a combination thereof. Firmware, software, and / or a combination thereof may be stored in a processor or memory.

[0259] The various elements of the embodiment can be described using terms such as the first and second. However, the various components according to the embodiment should not be limited by the above terms. These terms are only used to distinguish one element from another. For example, the first user input signal can be referred to as the second user input signal. Similarly, the second user input signal can be referred to as the first user input signal. The use of these terms should be interpreted as not departing from the scope of various embodiments. Both the first user input signal and the second user input signal are user input signals, but do not mean the same user input signal unless the context clearly stipulates otherwise. The terms used to describe the embodiment are only used to describe a specific embodiment and are not intended to limit the embodiment. As used in the description of the embodiment and the claims, unless the context clearly stipulates otherwise, the singular form "one", "one" and "the" include plural indicators. The expression "and / or" is used to include all possible combinations of items. Terms such as "including" or "having" are intended to indicate the presence of figures, numbers, steps, elements and / or components, and should be understood as not excluding the possibility of additional presence of figures, numbers, steps, elements and / or components.

[0260] As used herein, conditional expressions such as "if" and "when" are not limited to optional situations and are intended to be interpreted as performing relevant operations or interpreting relevant definitions according to specific conditions when specific conditions are met. Implementation methods may include changes / modifications within the scope of the claims and their equivalents. It will be apparent to those skilled in the art that various modifications and variations may be made in the present disclosure without departing from the spirit and scope of the present disclosure. Therefore, the present disclosure is intended to cover modifications and variations of the present disclosure as long as they fall within the scope of the appended claims and their equivalents.

[0261] Mode of the present disclosure

[0262] As described above, the relevant contents have been described in the best mode for carrying out the embodiment.

[0263] Industrial Applicability

[0264] As described above, the embodiments may be applied in whole or in part to 3D data transmission / reception devices and systems. It will be apparent to those skilled in the art that various changes or modifications may be made to the embodiments within the scope of the embodiments. Therefore, the embodiments are intended to cover modifications and variations as long as they fall within the scope of the appended claims and their equivalents.

Claims

1. A method for transmitting three-dimensional 3D data, the method comprising the following steps: Preprocess the input grid data; Encode the preprocessed grid data; as well as Send a bitstream containing the encoded mesh data.

2. The method according to claim 1, wherein: The steps of preprocessing the input grid data include the following steps: Generating simplified mesh data by simplifying the input mesh data; generating texture coordinates of each vertex in the simplified mesh data; and The simplified mesh data with the texture coordinates is subdivided, and then fitting subdivided mesh data similar to the input mesh data is generated by fitting.

3. The method according to claim 2, wherein: The step of generating the texture coordinates comprises the following steps: segmenting polygons or vertices constituting the simplified mesh data by combining polygons or vertices having similar characteristics based on the characteristics of the polygons or vertices of the simplified mesh data; Generating a mesh patch for the current frame based on the segmented polygons or vertex collection; and The mesh patch of the current frame is packed onto a two-dimensional 2D image based on the packing result of the mesh patch of the previous frame, and texture coordinates of each of the vertices of the simplified mesh data are generated.

4. The method according to claim 3, wherein: The step of packing the grid patches of the current frame onto a two-dimensional 2D image comprises the following steps: determining whether the previous frame has a grid patch that matches a current grid patch of the current frame; and Based on determining that the previous frame has a matching mesh patch, a mapping position of the current mesh patch on the 2D image is determined based on a mapping position of the matching mesh patch in the previous frame, and the current mesh patch is packed onto the determined mapping position on the 2D image.

5. The method according to claim 4, wherein: The current mesh patch is packed onto the 2D image to have the same or close mapping position as the matching mesh patch in the previous frame.

6. The method according to claim 4, wherein: The mesh patches of the current frame that correspond to the matching mesh patches in the previous frame are first packed onto the 2D image.

7. The method according to claim 4, wherein: The step of determining whether the previous frame has the matching mesh patch comprises: The mesh patch of the previous frame is determined to match the current mesh patch based on the mesh patch of the previous frame being in the same orientation as the current mesh patch and having a similar number of polygons and / or vertices as the current mesh patch.

8. The method according to claim 4, wherein: The steps to encode the preprocessed grid data include: Texture coordinates are regenerated based on the texture coordinates of each vertex in the simplified mesh data and the texture coordinates of each vertex in the input mesh data, and video encoding is performed.

9. A device for transmitting three-dimensional 3D data, the device comprising: A preprocessor configured to preprocess input grid data; an encoder configured to encode the preprocessed mesh data; as well as A transmitter is configured to transmit a bit stream containing encoded mesh data.

10. The device according to claim 9, wherein: The preprocessor comprises: a mesh simplification unit configured to generate simplified mesh data by simplifying the input mesh data; a parameterization unit configured to generate texture coordinates of each vertex in the simplified mesh data; and A fitting subdivision surface unit is configured to subdivide the simplified mesh data having the texture coordinates, and then generate fitting subdivision mesh data similar to the input mesh data by fitting.

11. The device according to claim 10, wherein: The parameterization unit comprises: a polygon / vertex segmentation unit configured to segment polygons or vertices constituting the simplified mesh data by combining polygons or vertices having similar characteristics based on the characteristics of the polygons or vertices of the simplified mesh data; a mesh patch segmentation unit configured to generate a mesh patch of a current frame based on a set of segmented polygons or vertices; and A mesh patch packer is configured to pack the mesh patch of the current frame onto a two-dimensional 2D image based on a packing result of the mesh patch of the previous frame, and generate texture coordinates of each of the vertices of the simplified mesh data.

12. The device according to claim 11, wherein The mesh patch packer performs operations, the operations comprising: determining whether the previous frame has a grid patch that matches a current grid patch of the current frame; and Based on determining that the previous frame has a matching mesh patch, a mapping position of the current mesh patch on the 2D image is determined based on a mapping position of the matching mesh patch in the previous frame, and the current mesh patch is packed onto the determined mapping position on the 2D image.

13. The device according to claim 11, wherein: The mesh patch packer is configured to: packing a current mesh patch onto the 2D image to have the same or close mapping position as a matching mesh patch in the previous frame; and The mesh patches of the current frame that correspond to the matching mesh patches in the previous frame are first packed onto the 2D image.

14. The device according to claim 11, wherein: The mesh patch packer determines that the mesh patch of the previous frame matches the current mesh patch based on the mesh patch of the previous frame being in the same orientation as the current mesh patch and having a similar number of polygons and / or vertices as the current mesh patch.

15. The apparatus according to claim 11, wherein: The encoder regenerates texture coordinates based on the texture coordinates of each vertex in the simplified mesh data and the texture coordinates of each vertex in the input mesh data, and performs video encoding.

Images