Mesh data transmission device, mesh data transmission method, mesh data reception device, and mesh data reception method

Abstract

A decoding method according to embodiments may comprise: a base mesh processing step for restoring a base mesh from a base mesh bitstream included in a bitstream; a packed video data processing step for restoring displacement information and attribute information by separating same from a packed video data bitstream included in the bitstream on the basis of signaling information; and a restoration step for restoring a mesh on the basis of the base mesh and the displacement information.

Description

Mesh data transmission device, mesh data transmission method, mesh data reception device, and mesh data reception method

[0001] The embodiments provide a method for providing 3D content to provide users with various services such as VR (Virtual Reality), AR (Augmented Reality), MR (Mixed Reality), and autonomous driving services.

[0002] Among 3D content, point cloud data and mesh data are collections of points in 3D space. However, the sheer number of points in 3D space makes it difficult to generate point cloud or mesh data.

[0003] That is, there is a problem that a lot of processing is required to transmit and receive 3D data with a large amount of points, such as point cloud data or mesh data.

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

[0005] The technical problem according to the embodiments is to provide a device and method for resolving latency and encoding / decoding complexity of mesh data.

[0006] A technical problem according to embodiments is to provide a device and method for efficiently performing encoding and decoding of packed video data in which displacement information and a texture map are packed into one frame.

[0007] However, the scope of the embodiments is not limited to the aforementioned technical tasks, and the scope of the embodiments may be expanded to other technical tasks that can be inferred by a person skilled in the art based on the entire contents of this document.

[0008] To achieve the above-described purpose and other advantages, a decoding method according to embodiments may include a step of receiving a bitstream including mesh data, and a step of decoding the mesh data.

[0009] According to embodiments, the step of decoding the mesh data may include a base mesh processing step of restoring a base mesh from a base mesh bitstream included in the bitstream, a packed video data processing step of separating and restoring displacement information and attribute information from a packed video data bitstream included in the bitstream based on signaling information, and a restoration step of restoring a mesh based on the base mesh and the displacement information.

[0010] According to embodiments, the packed video data processing step may include a step of scalably decoding packed video data from the packed video data bitstream based on a layer basis, and a step of separating and restoring displacement information and attribute information from the packed video data of the decoded target packed video frame based on the signaling information.

[0011] According to embodiments, the signaling information may include information for identifying a location of the displacement information within the target packed video frame.

[0012] According to embodiments, the signaling information may be carried via a Supplemental enhancement information (SEI) message.

[0013] According to embodiments, a decoding device may include a memory and at least one processor connected to the memory, wherein the at least one processor may be configured to receive a bitstream including mesh data and decode the mesh data.

[0014] According to embodiments, the at least one processor may include a base mesh processing unit that restores a base mesh from a base mesh bitstream included in the bitstream, a packed video data processing unit that separates and restores displacement information and attribute information from a packed video data bitstream included in the bitstream based on signaling information, and a mesh restoration unit that restores a mesh based on the base mesh and the displacement information.

[0015] According to embodiments, the packed video data processing unit can scalably decode packed video data from the packed video data bitstream based on a layer basis, and separate and restore displacement information and attribute information from the packed video data of the decoded target packed video frame based on the signaling information.

[0016] According to embodiments, the signaling information may include information for identifying a location of the displacement information within the target packed video frame.

[0017] According to embodiments, the signaling information may be carried via an SEI message.

[0018] According to embodiments, the encoding method may include the steps of encoding mesh data, and transmitting a bitstream including the encoded mesh data.

[0019] According to embodiments, the step of encoding the mesh data may include a step of encoding a base mesh generated by simplifying an original mesh to generate a base mesh bitstream, a step of generating displacement information based on the base mesh, a step of generating attribute information based on the original mesh and the displacement information, a step of packing the displacement information and the attribute information into one packed video frame in units of layers and scalably encoding the same to generate a packed video data bitstream, and a step of generating signaling information for restoration of the displacement information and the attribute information.

[0020] According to embodiments, the signaling information may include information for identifying a location of the displacement information within the target packed video frame.

[0021] According to embodiments, the signaling information may be carried via an SEI message.

[0022] According to embodiments, a computer program stored on a computer-readable recording medium can be combined with a computer, which is hardware, to perform the above method.

[0023] According to embodiments, a transmission method may include a step of obtaining a bitstream for image information, wherein the bitstream is generated based on a step of encoding mesh data and a step of transmitting a bitstream including the encoded mesh data, and a step of transmitting data including the bitstream.

[0024] The mesh data transmission method, mesh data transmission device, mesh data reception method, and mesh data reception device according to the embodiments can provide a quality 3D service.

[0025] The mesh data transmission method, mesh data transmission device, mesh data reception method, and mesh data reception device according to the embodiments can achieve various video codec methods.

[0026] The mesh data transmission method, mesh data transmission device, mesh data reception method, and mesh data reception device according to the embodiments can provide general-purpose 3D content such as autonomous driving services.

[0027] The mesh data transmission method, mesh data transmission device, mesh data reception method, and mesh data reception device according to the embodiments pack a texture map and displacement information into one frame and then encode it using a video codec, thereby combining a video codec used for displacement information compression and a video codec used for texture map compression into one, thereby obtaining the effect of increasing coding efficiency.

[0028] The mesh data transmission method, mesh data transmission device, mesh data reception method, and mesh data reception device according to the embodiments can efficiently provide a scalable coding service by minimizing synchronization problems between data by packing geometry data and texture data into one frame at a time.

[0029] The mesh data receiving method and the mesh data receiving device according to the embodiments can effectively decode and render scalable coded data in a manner such as in whole or selectively, depending on hardware constraints such as resources and displays of the receiving device and / or the intention and profile definition of the content creator, user, or receiver itself.

[0030] The drawings are included to further understand the embodiments, and the drawings illustrate the embodiments together with the description related to the embodiments. For a better understanding of the various embodiments described below, reference should be made to the following description of the embodiments in conjunction with the following drawings, in which like reference numerals correspond to corresponding parts throughout the drawings.

[0031] FIG. 1 illustrates a system for providing dynamic mesh content according to embodiments.

[0032] Figure 2 illustrates a V-MESH compression method according to embodiments.

[0033] Figure 3 illustrates pre-processing of V-MESH compression according to embodiments.

[0034] Figure 4 illustrates a mid-edge subdivision method according to embodiments.

[0035] Figure 5 illustrates a displacement generation process according to embodiments.

[0036] Figure 6 illustrates an intra-frame encoding process of V-MESH data according to embodiments.

[0037] Figure 7 illustrates an inter-frame encoding process of V-MESH data according to embodiments.

[0038] Figure 8 illustrates a lifting conversion process for displacement according to embodiments.

[0039] Figure 9 illustrates a process of packing transformation coefficients into a 2D image according to embodiments.

[0040] Figure 10 illustrates an attribute transfer process of a V-MESH compression method according to embodiments.

[0041] Figure 11 illustrates an intra-frame decoding process of V-MESH data according to embodiments.

[0042] Figure 12 shows an inter-frame decoding processor of V-MESH data.

[0043] Fig. 13 is a drawing showing an example of a transmitting device according to embodiments.

[0044] Fig. 14 is a drawing showing an example of a receiving device according to embodiments.

[0045] FIG. 15 is a diagram showing an example of a dynamic mesh bitstream structure encoded and transmitted in a transmitting device of the present disclosure.

[0046] FIG. 16 is a diagram showing an example of a syntax structure of a V3C unit payload (V3C_unit_payload) according to embodiments.

[0047] FIG. 17 is a drawing showing another example of a transmitting device according to embodiments.

[0048] Fig. 18 is a drawing showing another example of a receiving device according to embodiments.

[0049] FIG. 19 is a diagram showing an example of codec group profile components according to embodiments.

[0050] FIG. 20 is a diagram showing an example of a syntax structure of a component codec mapping SEI message according to embodiments.

[0051] FIG. 21 is a diagram showing an example of a syntax structure of scalable_packed_video_layer_info (payloadSize) according to embodiments.

[0052] FIG. 22 is a diagram showing another example of the syntax structure of scalable_packed_video_layer_info (payloadSize) according to embodiments.

[0053] Fig. 23 is a block diagram showing another example of a receiving device according to embodiments.

[0054] Figure 24 is a flowchart showing an example of a transmission method according to embodiments.

[0055] Figure 25 is a flowchart showing an example of a receiving method according to embodiments.

[0056] Preferred embodiments of the embodiments are described in detail, examples of which are illustrated in the accompanying drawings. The following detailed description, with reference to the accompanying drawings, is intended to illustrate preferred embodiments of the embodiments, rather than merely show embodiments that can be implemented according to the embodiments. The following detailed description includes details to provide a thorough understanding of the embodiments. However, it will be apparent to those skilled in the art that the embodiments may be practiced without these details.

[0057] While most of the terms used in the examples are commonly used in the field, some terms were arbitrarily selected by the applicant, and their meanings are described in detail in the following descriptions as needed. Therefore, the examples should be understood based on the intended meaning of the terms, not simply their names or meanings.

[0058] Recently, with the development of 3D data modeling and rendering technology, research on creating and processing 3D data is being conducted in various fields such as 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 point clouds, meshes, etc., depending on the representation format. Among these, a mesh is composed of geometric information expressing the coordinate values ​​of each vertex (or point), connection information indicating the connection relationship between vertices, a texture map expressing the color information of the mesh surface as 2D image data, and texture coordinates indicating mapping information between the surface of the mesh and the texture map. In the present disclosure, a mesh is defined as a dynamic mesh if one or more of the elements constituting the mesh change over time, and a static mesh if they do not change.

[0059] Because dynamic mesh data has a large amount of data for elements that constitute the mesh compared to two-dimensional image data, technologies have been developed to efficiently compress this large amount of mesh data to store and transmit it.

[0060] FIG. 1 illustrates a system for providing dynamic mesh content according to embodiments.

[0061] The system of FIG. 1 includes a transmitting device (100) and a receiving device (110) according to embodiments. The transmitting device (100) may include a mesh video acquisition unit (101), a mesh video encoder (102), a file / segment encapsulator (103), and a transmitter (104). The receiving device (110) may include a receiving unit (111), a file / segment decapsulator (112), a mesh video decoder (113), and a renderer (114). Each component of FIG. 1 may correspond to hardware, software, a processor, and / or a combination thereof. Hereinafter, the mesh data transmitting device according to embodiments may be interpreted as a term referring to a 3D data transmitting device or transmitting device (100), or a mesh video encoder (hereinafter, referred to as an encoder) (102). The mesh data receiving device according to the embodiments may be interpreted as a term referring to a 3D data receiving device or receiving device (110), or a mesh video decoder (hereinafter, decoder) (113).

[0062] The system of FIG. 1 can perform video-based dynamic mesh compression and decompression.

[0063] Advances in 3D capture, modeling, and rendering have enabled users to consume diverse forms of 3D content, such as AR, XR, metaverse, and holograms, across multiple platforms and devices. 3D content increasingly represents objects with greater precision and realism, enabling users to enjoy immersive experiences. To achieve this, the creation and use of 3D models requires a significant amount of data. Among various types of 3D content, 3D meshes are widely used for efficient data utilization and realistic object representation. Embodiments include a series of processing steps in a system that utilizes such mesh content.

[0064] First, the method of compressing dynamic mesh data starts from the V-PCC (Video-based point cloud compression) standard technology for point cloud data. Point cloud data is data that has color information at the coordinates (X, Y, Z) of a vertex (or point). In the present disclosure, the coordinates (i.e., position information) of a vertex are referred to as geometry information, the color information of a vertex is referred to as attribute information, and the geometry information and attribute information are referred to as vertex information or point cloud data. The vertex information to which connectivity information between vertices is added is referred to as mesh data. When creating content, it can be created in the form of mesh data from the beginning. Alternatively, it can be used by converting it into mesh data by adding connectivity information to point cloud data.

[0065] Currently, the MPEG standards body defines two types of dynamic mesh data: Category 1: Mesh data with texture maps as color information. Category 2: Mesh data with vertex colors as color information.

[0066] Mesh coding standards for Category 1 data are currently under development, and work on Category 2 data standards is also planned for the future. The overall process for providing mesh content services may include acquisition, encoding, transmission, decoding, rendering, and / or feedback, as shown in Figure 1.

[0067] To provide mesh content services, 3D data acquired through multiple cameras or specialized cameras can be processed into mesh data types through a series of processes and then converted into video. The generated mesh video is then transmitted through a series of processes, and the receiving end can then reprocess the received data into mesh video and render it. This allows mesh video to be presented to users, who can then interact with the mesh content according to their intended intent.

[0068] A mesh compression system may include a transmitting device (100) and a receiving device (110) as shown in FIG. 1. The transmitting device (100) may encode mesh video to output a bitstream, and transmit the bitstream to the receiving device (110) in the form of a file or streaming (streaming segment) via a digital storage medium or a network. The digital storage medium may include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, and SSD.

[0069] In the above transmitting device (100), the encoder may be called a mesh video / video / picture / frame encoding device, and in the receiving device (110), the decoder may be called a mesh video / video / picture / frame decoding device. The transmitter may be included in a mesh video encoder. The receiver may be included in a mesh video decoder. The renderer (114) may include a display unit, and the renderer and / or the display unit may be configured as separate devices or external components. The transmitting device (100) and the receiving device (110) may further include separate internal or external modules / units / components for a feedback process.

[0070] Mesh data represents the surface of an object as a number of polygons. Each polygon is defined by vertices in 3D space and connection information that describes how the vertices are connected. It can also contain vertex attributes such as vertex color and normal. Mapping information that allows the surface of the mesh to be mapped to a 2D planar area can also be included in the attributes of the mesh. The mapping can be described as a set of parameter coordinates, generally called UV coordinates or texture coordinates, associated with the mesh vertices. Meshes contain 2D attribute maps, which can be used to store high-resolution attribute information such as textures, normals, and displacement. Here, displacement can be used interchangeably with displacement, displacement information, or displacement vectors (i.e., displacement vectors).

[0071] The mesh video acquisition unit (101) may include processing 3D object data acquired through a camera, etc. into a mesh data type having the attributes described above through a series of processes and generating a video composed of such mesh data. The mesh video may have attributes of the mesh, such as vertices, polygons, connection information between vertices, colors, normals, etc., that may change over time. A mesh video having attributes and connection information that change over time in this way may be expressed as a dynamic mesh video.

[0072] A mesh video encoder (102) can encode an input mesh video into one or more video streams. One video can include multiple frames, and one frame can correspond to a still image / picture. In this document, a mesh video can include a mesh image / frame / picture, and a mesh video can be used interchangeably with a mesh image / frame / picture. The mesh video encoder (102) can perform a Video-based Dynamic Mesh (V-Mesh) Compression procedure. The mesh video encoder (102) can perform a series of procedures such as prediction, transformation, quantization, and entropy coding for compression and coding efficiency. The encoded data (encoded video / image information) can be output in the form of a bitstream.

[0073] The file / segment encapsulator (103) can encapsulate encoded mesh video data and / or mesh video-related metadata in the form of a file, etc. Here, the mesh video-related metadata may be received from a metadata processing unit, etc. The metadata processing unit may be included in the mesh video encoder (102) or may be configured as a separate component / module. The file / segment encapsulator (103) can encapsulate the corresponding data in a file format such as ISOBMFF, or process it in the form of other DASH segments, etc. The file / segment encapsulator (103) may include mesh video-related metadata in the file format according to an embodiment. The mesh video metadata may be included in boxes at various levels in the ISOBMFF file format, for example, or may be included as data in a separate track within the file. Depending on the embodiment, the file / segment encapsulator (103) may encapsulate the mesh video related metadata itself into a file.

[0074] The transmission processing unit can process encapsulated mesh video data for transmission according to the file format. The transmission processing unit can be included in the transmission unit (104) or can be configured as a separate component / module. The transmission processing unit can process mesh video data according to any transmission protocol. The processing for transmission can include processing for transmission through a broadcast network or processing for transmission through broadband. According to an embodiment, the transmission processing unit can receive not only mesh video data but also mesh video-related metadata from the metadata processing unit and process it for transmission.

[0075] The transmission unit (104) can transmit encoded video / image information or data output in the form of a bitstream to the reception unit (111) of the reception device (110) via a digital storage medium or network in the form of a file or streaming. The digital storage medium can include various storage media such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc. The transmission unit (104) can include an element for generating a media file through a predetermined file format and can include an element for transmission via a broadcasting / communication network. The reception unit (111) can extract the bitstream and transmit it to a decoding device.

[0076] The receiving unit (111) can receive mesh video data transmitted by a mesh data transmission device. Depending on the channel through which it is transmitted, the receiving unit (111) can receive mesh video data through a broadcast network, through a broadband, or through a digital storage medium.

[0077] The receiving processing unit can perform processing according to the transmission protocol on the received mesh video data. The receiving processing unit can be included in the receiving unit (111) or can be configured as a separate component / module. In order to correspond to the processing performed for transmission on the transmitting side, the receiving processing unit can perform the reverse process of the aforementioned transmission processing unit. The receiving processing unit can transfer the acquired mesh video data to the file / segment decapsulator (112) and transfer the acquired mesh video-related metadata to the metadata parser. The mesh video-related metadata acquired by the receiving processing unit can be in the form of a signaling table.

[0078] The file / segment decapsulator (112) can decapsulate mesh video data in the form of a file received from a receiving processing unit. The file / segment decapsulator (112) can decapsulate files according to ISOBMFF, etc., to obtain a mesh video bitstream or mesh video-related metadata (metadata bitstream). The obtained mesh video bitstream can be transmitted to the mesh video decoder (113), and the obtained mesh video-related metadata (metadata bitstream) can be transmitted to the metadata processing unit. The mesh video bitstream may include metadata (metadata bitstream). The metadata processing unit may be included in the mesh video decoder (113) or may be configured as a separate component / module. The mesh video-related metadata obtained by the file / segment decapsulator (112) may be in the form of a box or track within a file format. The file / segment decapsulator (112) may receive metadata required for decapsulation from the metadata processing unit, if necessary. The mesh video related metadata may be passed to the mesh video decoder (113) and used in the mesh video decoding procedure, or may be passed to the renderer (114) and used in the mesh video rendering procedure.

[0079] The mesh video decoder (113) can receive a bitstream and perform a reverse operation corresponding to the operation of the mesh video encoder (102) to decode the video / image. The decoded mesh video / image can be displayed through the display unit of the renderer (114). The user can view all or part of the rendered result through a VR / AR display or a general display.

[0080] The feedback process may include a process of transmitting various feedback information that may be acquired during the rendering / display process to the transmitter or to the decoder on the receiver. Interactivity may be provided in mesh video consumption through the feedback process. Depending on the embodiment, head orientation information, viewport information indicating the area that the user is currently viewing, etc. may be transmitted during the feedback process. Depending on the embodiment, the user may interact with things implemented in the VR / AR / MR / autonomous driving environment, in which case information related to the interaction may be transmitted to the transmitter or the service provider during the feedback process. Depending on the embodiment, the feedback process may not be performed.

[0081] Head orientation information can refer to information about the user's head position, angle, and movement. Based on this information, information about the area the user is currently viewing within the mesh video, i.e. viewport information, can be calculated.

[0082] Viewport information can be information about the area the user is currently viewing in the mesh video. This can be used to perform gaze analysis to determine how the user consumes the mesh video, which area of ​​the mesh video they are gazing at, and for how long. Gaze analysis can be performed on the receiving side and transmitted to the transmitting side through a feedback channel. Devices such as VR / AR / MR displays can extract the viewport area based on the user's head position / orientation, the vertical or horizontal FOV supported by the device, etc.

[0083] Depending on the embodiment, the aforementioned feedback information may not only be transmitted to the transmitter but may also be consumed by the receiver. That is, the aforementioned feedback information may be utilized to perform decoding, rendering, and other processes on the receiver. For example, head orientation information and / or viewport information may be utilized to preferentially decode and render only the mesh video for the area currently being viewed by the user.

[0084] This document relates to embodiments of dynamic mesh video compression as described above. The method / embodiment disclosed in this document can be applied to the Video-based Dynamic Mesh Compression (V-Mesh) standard of the Moving Picture Experts Group (MPEG) or the next-generation video / image coding standard. Dynamic mesh video compression is a method for processing mesh connection information and attributes that change over time, and it can perform lossy and lossless compression for various applications such as real-time communication, storage, free-viewpoint video, and AR / VR.

[0085] The dynamic mesh video compression method described below is based on MPEG's V-Mesh method.

[0086] In this document, picture / frame can generally mean a unit representing one video of a specific time period.

[0087] A pixel or pel can refer to the smallest unit that constitutes a picture (or image). Additionally, the term "sample" can be used as a counterpart to a pixel. A sample can generally represent a pixel or a pixel value, and can represent only the pixel / pixel value of the luma component, only the pixel / pixel value of the chroma component, or only the pixel / pixel value of the depth component.

[0088] A unit may represent a basic unit of image processing. A unit may include at least one of a specific region of a picture and information related to the region. In some cases, the term "unit" may be used interchangeably with terms such as "block" or "area." In general, an MxN block may include a set (or array) of samples (or sample array) or transform coefficients consisting of M columns and N rows.

[0089] As described above, the encoding process of Fig. 1 is as follows.

[0090] That is, the video-based dynamic mesh compression (V-Mesh) compression method can provide a method of compressing dynamic mesh video data based on 2D video codecs such as HEVC (High Efficiency Video Coding) and VVC (Versatile Video Coding). The V-Mesh compression process receives the following data as input and performs compression.

[0091] Input mesh: Contains the 3D coordinates of the vertices that make up the mesh, normal information for each vertex, mapping information that maps the mesh surface to a 2D plane, and connection information between the vertices that make up the surface. The mesh surface can be expressed as triangles or more polygons, and connection information between the vertices that make up each surface is stored according to a set shape. The input mesh can be saved in the OBJ file format.

[0092] Attribute map: (Hereinafter, texture map is also used in the same meaning): Contains information about the attributes of the mesh (color, normal, displacement, etc.), and stores data in the form of a mapping of the surface of the mesh onto a 2D image. Mapping which part (surface or vertex) of the mesh each data of this attribute map corresponds to is based on the mapping information contained in the input mesh. Since the attribute map has data for each frame of the mesh video, it can also be expressed as an attribute map video. The attribute map in the V-Mesh compression method mainly contains the color information of the mesh, and is saved in an image file format (PNG, BMP, etc.).

[0093] Material Library File: Contains information about the material attributes used in a mesh, and in particular, information that links the input mesh to its corresponding attribute map. It is saved in the Wavefront Material Template Library (MTL) file format.

[0094] In the V-Mesh compression method, the following data and information can be generated through the compression process.

[0095] Base mesh: The input mesh is simplified (decimated) through a pre-processing process, thereby expressing the objects of the input mesh using the minimum number of vertices determined by the user's standards.

[0096] Displacement: Displacement information used to express the input mesh as similarly as possible to the base mesh, and is expressed in the form of 3D coordinates.

[0097] Atlas information: This is the metadata required to reconstruct a mesh using base mesh, displacement, and attribute map information. It can be created and utilized as sub-mesh units (such as patches) that make up the mesh.

[0098] Referring to FIGS. 2 to 7, a method for encoding mesh position information (or vertex position information) is described, and referring to FIGS. 6 to 10, etc., a method for encoding attribute information (attribute map) by restoring mesh position information is described.

[0099] Figure 2 illustrates a V-MESH compression method according to embodiments.

[0100] Fig. 2 illustrates the encoding process of Fig. 1, and the encoding process may include a pre-processing process and an encoding process. The mesh video encoder (102) of Fig. 1 may include a pre-processor (200) and an encoder (201) as in Fig. 2. In addition, the transmitting device of Fig. 1 may be broadly referred to as an encoder, and the mesh video encoder (102) of Fig. 1 may be referred to as an encoder. The V-Mesh compression method may include a pre-processing process (Pre-processing, 200) and an encoding process (Encoding, 201) as in Fig. 2. The pre-processor (200) of Fig. 2 may be located in front of the encoder (201) of Fig. 2. The pre-processor (200) and the encoder (201) of Fig. 2 may be referred to as a single encoder.

[0101] The pre-processor (200) can receive a static of a dynamic mesh (M(i)) and / or an attribute map (A(i)). The pre-processor (200) can generate a base mesh (m(i)) and / or a displacement (or displacement) (d(i)) through pre-processing. The pre-processor (200) can receive feedback information from the encoder (201) and generate the base mesh and / or the displacement based on the feedback information.

[0102] The encoder (201) can receive a base mesh (m(i)), a displacement (d(i)), a static of a dynamic mesh (M(i)), and / or an attribute map (A(i)). In the present disclosure, at least one of the base mesh (m(i)), the displacement (d(i)), the static of a dynamic mesh (M(i)), and / or the attribute map (A(i)) can be referred to as mesh-related data. The encoder (201) can encode the mesh-related data to generate a compressed bitstream.

[0103] Figure 3 illustrates a pre-processing process of V-MESH compression according to embodiments.

[0104] Fig. 3 illustrates the configuration and operation of the preprocessor of Fig. 2. In Fig. 3, the input mesh may include a static of a dynamic mesh (M(i)) and / or an attribute map (A(i)). In addition, the input mesh may include three-dimensional coordinates of vertices constituting the mesh, normal information of each vertex, mapping information for mapping the mesh surface to a 2D plane, connection information between vertices constituting the surface, etc.

[0105] Fig. 3 shows a process of performing pre-processing on an input mesh. The pre-processing process (200) may largely include four steps: 1) GoF (Group of Frame) generation, 2) Mesh Decimation, 3) UV parameterization, and 4) Fitting subdivision surface (300). According to embodiments, GoF generation may be referred to as a GoF generation process or a GoF generation unit, mesh simplification may be referred to as a mesh simplification process or a mesh simplification unit, UV parameterization may be referred to as a UV parameterization process or a UV parameterization unit, and the fitting subdivision surface may be referred to as a fitting subdivision surface process or a fitting subdivision surface unit. The pre-processor (200) can generate displacement and / or base meshes from the received input mesh and transmit them to the encoder (201). The pre-processor (200) can transmit GoF information associated with GoF generation to the encoder (201).

[0106] Below, each step of Fig. 3 is described.

[0107] GoF Generation: This is the process of generating a reference structure for mesh data. If the number of vertices, the number of texture coordinates, the vertex connection information, and the texture coordinate connection information of the mesh of the previous frame and the current mesh are all the same, the previous frame can be set as the reference frame. That is, 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, intra frame encoding is performed for the corresponding frame.

[0108] Mesh Decimation: This process simplifies the input mesh to create a simplified mesh, or base mesh. Vertices to be removed from the original mesh are selected based on user-defined criteria, and the selected vertices and the triangles connected to them can be removed.

[0109] In the process of performing mesh simplification (Mesh decimation), the input mesh (voxelized), target triangle ratio (TTR), and minimum triangle component (CCCount) information are passed as input, and the simplified mesh (decimated mesh) can be obtained as output. In this process, connected triangle components smaller than the set minimum triangle component (CCCount) can be removed.

[0110] UV parameterization: This is the process of mapping a 3D surface of a decimated mesh into a texture domain. Parameterization can be performed using the UVAtlas tool. This process generates mapping information, which indicates where each vertex of the decimated mesh can be mapped to on a 2D image. This mapping information is expressed and stored as texture coordinates, and through this process, the final base mesh is created.

[0111] Fitting subdivision surface (300): This is a process of performing subdivision on a decimated mesh (i.e., a simplified mesh having texture coordinates). The displacement and base mesh generated through this process are output to the encoder (201). A user-defined method, such as a mid-edge method, may be applied as the subdivision method. A fitting process is performed so that the input mesh and the mesh on which the subdivision has been performed become similar to each other. In the present disclosure, the mesh on which the fitting process has been performed is referred to as a fitted subdivision mesh (or fitted subdivision mesh).

[0112] Figure 4 illustrates a mid-edge subdivision method according to embodiments.

[0113] Figure 4 illustrates the mid-edge method of the fitting subdivision surface described in Figure 3. Referring to Figure 4, an original mesh containing four vertices is subdivided to generate a sub-mesh. A sub-mesh can be generated by creating a new vertex in the middle of the edge between the vertices. Then, a fitting process is performed so that the input mesh and the sub-mesh become similar to each other, thereby generating a fitted sub-division mesh.

[0114] When a fitted subdivided mesh (hereinafter referred to as a fitted subdivided mesh) is generated, displacement is calculated using this result and a pre-compressed and decoded base mesh (hereinafter referred to as a reconstructed base mesh). That is, the reconstructed base mesh is subdivided in the same way as the fitting subdivision surface. The difference in position of each vertex between this result and the fitted subdivided mesh is the displacement for each vertex. Since displacement represents the position difference in three-dimensional space, it is also expressed as a value in the (x, y, z) space of a Cartesian coordinate system. Depending on the user input parameters, the (x, y, z) coordinate values ​​can be converted to (normal, tangential, bi-tangential) coordinate values ​​of the local coordinate system.

[0115] Fig. 5 illustrates a displacement generation process according to embodiments. The displacement generation process of Fig. 5 may be performed in a pre-processor (200) or in an encoder (201).

[0116] FIG. 5 illustrates in detail the displacement calculation method of the fitting subdivision surface (300) as described in FIG. 4.

[0117] An encoder and / or pre-processor according to embodiments may include 1) a subdivision unit, 2) a local coordinate system calculation unit, and 3) a displacement calculation unit. The subdivision unit may perform subdivision on a reconstructed base mesh to generate a subdivided reconstructed base mesh. Here, the restoration of the base mesh may be performed in the pre-processor (200) or in the encoder (201). The local coordinate system calculation unit may receive a fitted subdivision mesh and a subdivided reconstructed base mesh, and may convert a coordinate system of the mesh into a local coordinate system based on the fitted subdivision mesh and the subdivided reconstructed base mesh. The local coordinate system calculation operation may be optional. The displacement calculation unit may calculate a positional difference between the fitted subdivision mesh and the subdivided reconstructed base mesh. For example, a positional difference value between vertices of two input meshes may be generated. The vertex positional difference value becomes a displacement.

[0118] The mesh data transmission method and device according to the embodiments can encode mesh data as follows. Mesh data is a term including point cloud data. Point cloud data (which may be referred to as point cloud for short) according to the embodiments can refer to data including vertex coordinates (or geometry information) and color information (or attribute information). In addition, geometry images, attribute images, occupancy maps, and additional information (or patch information) generated through patch generation and packing based on vertex coordinates and color information are also referred to as point cloud data. Therefore, point cloud data including connection information can be referred to as mesh data. In this document, point cloud and mesh data can be used interchangeably.

[0119] The V-Mesh compression (reconstruction) method according to the embodiments may include intra frame encoding (Fig. 6) and inter frame encoding (Fig. 7).

[0120] Based on the results of the GoF generation described above, intra-frame encoding or inter-frame encoding is performed. In the case of intra-encoding, the data to be compressed may be a base mesh, displacement, attribute map, etc. In the case of inter-encoding, the data to be compressed may be a displacement, attribute map, and a motion field between a reference base mesh and the current base mesh.

[0121] Fig. 6 illustrates an intra-frame encoding process of a V-MESH compression method according to embodiments. Each component for the intra-frame encoding process of Fig. 6 corresponds to hardware, software, a processor, and / or a combination thereof.

[0122] The encoding process of FIG. 6 details the encoding of the mesh video encoder (102) of FIG. 1. That is, it shows the configuration of the mesh video encoder (102) when the encoding of FIG. 1 is an intra-frame method. The encoder of FIG. 6 may include a pre-processor (200) and / or an encoder (201). The pre-processor (200) and encoder (201) of FIG. 6 may correspond to the pre-processor (200) and encoder (201) of FIG. 3.

[0123] The preprocessor (200) can receive an input mesh and perform the preprocessing described above. The preprocessing can generate a base mesh and / or a fitted subdivision mesh.

[0124] The quantizer (411) of the encoder (201) can quantize the base mesh and / or the fitted subdivided mesh. The static mesh encoder (412) can encode the static mesh (i.e., the quantized base mesh) and generate a bitstream (i.e., a compressed base mesh bitstream) including the encoded base mesh. The static mesh decoder (413) can decode the encoded static mesh (i.e., the encoded base mesh). The inverse quantizer (414) can inversely quantize the quantized static mesh (i.e., the base mesh) to output a reconstructed (or restored) base mesh. The displacement calculation unit (415) can generate displacements (or displacements) based on the reconstructed static mesh (i.e., the base mesh) and the fitted subdivided mesh. According to embodiments, the displacement calculation unit (415) calculates displacement, which is the position difference between each vertex of the subdivided base mesh and the fitted subdivided mesh after subdividing (or refining) the restored base mesh. In other words, the displacement is a displacement vector, which is the position difference between the vertices of the two meshes so that the fitted subdivided (or refining) mesh becomes similar to the original mesh. The forward linear lifting unit (416) can perform lifting transformation on the input displacement to generate lifting coefficients (or transform coefficients). The quantizer (417) can quantize the lifting coefficients. The image packing unit (418) can pack an image based on the quantized lifting coefficients. The video encoder (419) can encode the packed image. That is, the quantized lifting coefficients are packed into one frame as a 2D image by the image packing unit (418), compressed through the video encoder (419), and output as a displacement bitstream (i.e., compressed displacement bitstream).

[0125] A video decoder (420) decodes a compressed displacement bitstream. An image unpacking unit (421) can perform unpacking on the decoded displacement frame to output quantized lifting coefficients. A dequantizer (422) can dequantize the quantized lifting coefficients. An inverse linear lifting unit (423) applies inverse lifting to the inverse quantized lifting coefficients to generate restored displacement. A mesh restoration unit (424) reconstructs and deforms a mesh using the restored displacement output from the inverse linear lifting unit (423) and the restored base mesh (or subdivided restored base mesh) output from the inverse quantization unit (414). The present disclosure refers to the reconstructed and deformed mesh as a restored deformed mesh.

[0126] The attribute transfer (425) receives an input mesh and / or an input attribute map, and regenerates an attribute map based on the restored deformed mesh. The attribute map refers to a texture map corresponding to attribute information among mesh data components, and in the present disclosure, the attribute map and the texture map may be used interchangeably. The push-pull padding (426) may pad data in the attribute map based on the push-pull method. The color space conversion unit (427) may convert the space of the color component of the attribute map. For example, the attribute map may be converted from an RGB color space to a YUV color space. The video encoder (428) may encode the attribute map and output it as a compressed attribute bitstream.

[0127] A multiplexer (430) can generate a compressed bitstream by multiplexing a compressed base mesh bitstream, a compressed displacement bitstream, and a compressed attribute bitstream.

[0128] In Fig. 6, the displacement calculation unit (415) may be included in the pre-processor (200). In addition, at least one of the quantizer (411), the static mesh encoder (412), the static mesh decoder (413), and the inverse quantizer (414) may be included in the pre-processor (200).

[0129] As described in FIG. 6, the intra-frame encoding method includes base mesh encoding (also called static mesh encoding). That is, when performing intra-frame encoding on the current input mesh frame, the base mesh generated in the pre-processing process of the pre-processor (200) can be encoded using a static mesh compression technology in a static mesh encoder (412) after undergoing a quantization process in a quantizer (411). In the V-Mesh compression method, for example, Draco technology is applied to base mesh encoding, and vertex position information, mapping information (texture coordinates), vertex connection information, etc. of the base mesh become compression targets.

[0130] The encoder of Fig. 6 generates a bitstream by compressing the base mesh, displacement, and attributes within the frame, and the encoder of Fig. 7 generates a bitstream by compressing the motion, displacement, and attributes between the current frame and the reference frame.

[0131] Fig. 7 illustrates an inter-frame encoding process of a V-MESH compression method according to embodiments. Each component for the inter-frame encoding process of Fig. 7 corresponds to hardware, software, a processor, and / or a combination thereof.

[0132] The encoding process of Fig. 7 details the encoding of Fig. 1. That is, it shows the configuration of an encoder when the encoding of Fig. 1 is an inter-frame method. The encoder of Fig. 7 may include a pre-processor (200) and / or an encoder (201). The pre-processor (200) and encoder (201) of Fig. 7 may correspond to the pre-processor (200) and encoder (201) of Fig. 3.

[0133] For a description of the components corresponding to the encoding operation of FIG. 6 among the encoding operations of FIG. 7, refer to the description of FIG. 6. That is, the operation of the quantizer (511), displacement calculation unit (515), wavelet transformer (516), quantizer (517), image packing unit (518), video encoder (519), video decoder (520), image unpacking unit (521), inverse quantizer (522), inverse wavelet transformer (523), mesh restoration unit (524), attribute transfer (525), push-pull padding (526), ​​color space conversion unit (527), video encoder (528), and multiplexer (530) of FIG. 7 is similar to that of the quantizer (411), static mesh encoder (412), static mesh decoder (413), inverse quantizer (414), displacement calculation unit (415), forward linear lifting unit (416), quantizer (417), image Since the operations described in the packing unit (418), video encoder (419), video decoder (420), image unpacking unit (421), inverse quantizer (422), inverse linear lifting unit (423), mesh restoration unit (424), attribute transfer (425), push-pull padding (426), color space conversion unit (427), video encoder (428), and multiplexer (430) are the same or similar, a detailed description thereof is omitted in FIG. 7 to avoid redundant description.

[0134] In Fig. 7, for inter-frame based encoding, the motion encoder (512) can obtain a motion vector between the two base meshes based on the restored quantized reference base mesh and the quantized current base mesh, and then encode the motion vector to output a compressed motion bitstream. The motion encoder (512) can be referred to as a motion vector encoder. The base mesh restoration unit (513) can restore the base mesh based on the restored quantized reference base mesh and the encoded motion vector. The restored base mesh is dequantized in the dequantizer (514) and then output to the displacement calculation unit (515).

[0135] In Fig. 7, the displacement calculation unit (515) may be included in the pre-processor (200). In addition, at least one of the quantizer (511), the motion encoder (512), the base mesh restoration unit (513), and the inverse quantizer (514) may be included in the pre-processor (200).

[0136] As described in Fig. 7, the inter-frame encoding method may include motion field encoding (also called motion vector encoding). Inter-frame encoding may be performed when a one-to-one correspondence of vertices is established between a reference mesh and a current input mesh, and only the position information of the vertices is different. When performing inter-frame encoding, instead of compressing the base mesh, the difference between the vertices of the reference base mesh and the current base mesh, i.e., the motion field (also called motion vector), may be calculated and encoded to encode this information. The reference base mesh is the result of quantizing the already decoded base mesh data and is determined according to the reference frame index determined in the GoF generation. The motion field may also be encoded as a value. Alternatively, the predicted motion field can be calculated by averaging the motion fields of the restored vertices among the vertices connected to the current vertex, and the residual motion field, which is the difference between the predicted motion field value and the motion field value of the current vertex, can be encoded. This residual motion field value can be encoded using entropy coding.The process of encoding displacement and attribute maps, excluding the motion field encoding process of inter frame encoding, is the same as the structure of the intra frame encoding method except for the base mesh encoding.

[0137] Figure 8 illustrates a lifting conversion process for displacement according to embodiments.

[0138] Figure 9 illustrates a process of packing transformation coefficients (or lifting coefficients) according to embodiments into a 2D image.

[0139] Figures 8 and 9 illustrate the process of transforming displacement and packing transform coefficients of the encoding process of Figures 6 and 7, respectively.

[0140] The encoding method according to the embodiments includes displacement encoding.

[0141] After base mesh encoding and / or motion field encoding, a reconstructed base mesh is generated through restoration and dequantization, and the displacement between the result of performing subdivision on the reconstructed base mesh and the fitted subdivided mesh generated through the fitting subdivision surface can be calculated (see 415 in FIG. 6 or 515 in FIG. 7). For effective encoding, a data transform process such as wavelet transform can be applied to the displacement information (see 416 in FIG. 6 or 516 in FIG. 7).

[0142] FIG. 8 shows a process of transforming displacement information using a lifting transform in the forward linear lifting unit (416) of FIG. 6 or the wavelet transformer (516) of FIG. 7. For example, a linear wavelet-based lifting transform may be performed. The transform coefficients generated through the transform process are quantized in a quantizer (417 or 517) and then packed into a 2D image through an image packing unit (418 or 518) as in FIG. 9. The transform coefficients are configured as one block for every 256 (= 16×16) units, and each block can be packed in a z-scan order. The horizontal number of blocks is fixed to 16, but the vertical number of blocks can be determined according to the number of vertices of the subdivided base mesh. Transform coefficients can be packed by aligning them with Morton codes within a single block. The packed images generate displacement videos for each GoF unit, and these displacement videos can be encoded using a conventional video compression codec in a video encoder (419 or 519).

[0143] Referring to FIG. 8, the base mesh (original) may include vertices and edges for LoD0. A first subdivision mesh generated by dividing (or subdividing) the base mesh includes vertices generated by further dividing (or subdividing) edges of the base mesh. The first subdivision mesh includes vertices for LoD0 and vertices for LoD1. LoD1 includes the subdivided vertices and the vertices of the base mesh (LoD0). The first subdivision mesh may be further divided (or subdivided) to generate a second subdivision mesh. The second subdivision mesh includes LoD2. LoD2 includes base mesh vertices (LoD0), LoD1 including vertices further divided (or subdivided) from LoD0, and vertices further divided (or subdivided) from LoD1. LoD is a level of detail that indicates the degree of detail of mesh data content. As the level index increases, the distance between vertices becomes closer and the level of detail increases. In other words, the smaller the LoD value, the lower the detail of the mesh data content, and the larger the LoD value, the higher the detail of the mesh data content. LoD N contains the vertices included in the previous LoDN-1 as is. When a mesh (or vertex) is further divided through subdivision, the mesh can be encoded based on a prediction and / or update method by considering the previous vertices v1, v2 and the subdivided vertex v. Instead of directly encoding information about the current LoD N, a residual value between the previous LoD N-1 can be generated and the mesh can be encoded using the residual value to reduce the size of the bitstream. The prediction process means the operation of predicting the current vertex v using the previous vertices v1 and v2. Since adjacent subdivision meshes have similar data, this property can be utilized for efficient encoding.Current vertex position information is predicted as a residual of previous vertex position information, and the previous vertex position information is updated through the residual. In the present disclosure, vertex, apex, and point may be used with the same meaning. In addition, LoDs may be defined during the subdivision process of the base mesh. According to embodiments, the subdivision process of the base mesh may be performed in the pre-processor (200) or in a separate component / module.

[0144] Referring to FIG. 9, a vertex has a transform coefficient (also called a lifting coefficient) generated through a lifting transformation. The transform coefficient of a vertex related to a lifting transformation can be packed into an image by an image packing unit (418 or 518) and then encoded by a video encoder (419 or 519).

[0145] Figure 10 illustrates an attribute transfer process of a V-MESH compression method according to embodiments.

[0146] According to the embodiments, FIG. 10 shows the detailed operation of the attribute transfer (425 or 525) of the encoding of FIG. 6, FIG. 7, etc.

[0147] Encoding according to embodiments includes attribute map encoding. According to embodiments, attribute map encoding may be performed in the video encoder (428) of FIG. 6 or the video encoder (528) of FIG. 7.

[0148] According to embodiments, in the present disclosure, the encoder compresses information about the input mesh through base mesh encoding (i.e., intra encoding), motion field encoding (i.e., inter encoding), and displacement encoding. In the encoding process, the compressed input mesh is restored through base mesh decoding (intra frame), motion field decoding (inter frame), and displacement video decoding processes, and the restored result, the reconstructed deformed mesh (hereinafter referred to as Recon. deformed mesh), is used to compress the input attribute map as shown in FIGS. 6 and 7. The reconstructed deformed mesh (Recon. deformed mesh) has position information of vertices, texture coordinates, and corresponding connection information, but does not have color information corresponding to the texture coordinates. Therefore, as shown in Fig. 10, in the V-Mesh compression method, a new attribute map having color information corresponding to the texture coordinates of the reconstructed deformed mesh is regenerated through the attribute transfer process of attribute transfer (425 or 525).

[0149] According to embodiments, attribute transfer (425 or 525) first checks whether each point P(u, v) of a 2D texture domain belongs to a texture triangle of a reconstructed deformed mesh, and if it exists in a texture triangle T, the barycentric coordinate of P(u, v) according to the triangle T ( , , ) is calculated. And the 3D vertex positions of triangle T and ( , , ) is used to compute the 3D coordinates M(x, y, z) of P(u, v). Find the vertex coordinates M'(x', y', z') and the triangle T' containing this vertex that corresponds to the most similar position to the calculated M(x, y, z) in the input mesh domain. Then, the center of mass coordinates of M'(x', y', z') in this triangle T' ( ', ', ') is calculated. The texture coordinates corresponding to the three vertices of Triangle T' and ( ', ', ') is used to calculate the texture coordinates (u', v'), and the color information corresponding to these coordinates is found in the input attribute map. The color information found in this way is immediately assigned to the pixel location (u, v) of the new attribute map. If P(u, v) does not belong to any triangle, the pixel at that location in the new attribute map can be filled with a color value using a padding algorithm, such as the push-pull algorithm of push-pull padding (426 or 526).

[0150] The new attribute map generated through attribute transfer (425 or 525) is grouped into GoF units to form an attribute map video, which is compressed using the video codec of the video encoder (428 or 528).

[0151] Referring to Figure 10, the reference relationship between the input mesh, the input attribute map, the reconstructed deformed mesh, and the regenerated attribute map can be seen.

[0152] The decoding process of Fig. 1 can perform the reverse process of the corresponding process of the encoding process of Fig. 1. The specific decoding process is as follows.

[0153] FIG. 11 illustrates an intra-frame decoding (or intra-decoding) process of V-Mesh technology according to embodiments.

[0154] Fig. 11 illustrates the configuration and operation of the mesh video decoder (113) of the receiving device of Fig. 1. In addition, Fig. 11 can restore mesh data by performing the reverse process of the intra-frame encoding process of Fig. 6. Each component for the intra-frame decoding process of Fig. 11 corresponds to hardware, software, and / or a combination thereof.

[0155] First, the bitstream (i.e., compressed bitstream) received and input to the demultiplexer (611) of the intra frame decoding unit (610) can be separated into a mesh substream, a displacement substream, an attribute map substream, and a substream containing patch information of the mesh, such as V-PCC / V3C. The term V-PCC (Video-based Point Cloud Compression) used in this document can be used with the same meaning as V3C (Visual Volumetric Video-based Coding), and the two terms can be used interchangeably. Therefore, the term V-PCC in this document can be interpreted as the term V3C.

[0156] According to embodiments, the mesh sub-stream may be input to a static mesh decoder (612) and decoded, the displacement sub-stream may be input to a video decoder (613) and decoded, and the attribute map sub-stream may be input to a video decoder (617) and decoded.

[0157] According to embodiments, the mesh sub-stream is decoded through a decoder (612) of a static mesh codec used in encoding, such as Google Draco, and as a result, a reconstructed quantized base mesh, for example, connection information, vertex geometry information, vertex texture coordinates, etc. of the base mesh can be reconstructed.

[0158] According to embodiments, the displacement sub-stream is decoded into displacement video through a decoder (613) of a video compression codec used in encoding, and is restored as displacement information for each vertex (i.e., Recon. displacements) through an image unpacking process of an image unpacking unit (614), an inverse quantization process of an inverse quantizer (615), and an inverse transform process of an inverse linear lifting unit (616).

[0159] According to embodiments, the base mesh restored by the static mesh decoder (612) is inverse quantized by the inverse quantizer (620) and then output to the mesh restoration unit (630). The mesh restoration unit (630) reconstructs and restores the deformed mesh (i.e., decoded mesh) through the restored displacement output from the inverse linear lifting unit (616) and the restored base mesh output from the inverse quantizer (620). That is, the inverse quantized restored base mesh is combined with the restored displacement information to generate the final decoded mesh. In the present disclosure, the final decoded mesh is referred to as a reconstructed deformed mesh.

[0160] According to embodiments, an attribute map sub-stream is decoded through a decoder (617) corresponding to a video compression codec used in encoding, and then restored to a final attribute map (i.e., decoded attribute map) through a color conversion unit (640) through processes such as color format conversion and color space conversion.

[0161] According to embodiments, the restored decoded mesh and decoded attribute map can be utilized by the receiver as final mesh data that can be utilized by the user.

[0162] Referring to FIG. 11, the received compressed bitstream includes patch information, a mesh substream, a displacement substream, and an attribute map substream. A substream is interpreted as a term referring to a part of a bitstream included in a bitstream. The bitstream includes patch information (data), mesh information (data), displacement information (data), and attribute map information (data).

[0163] As described above, the decoder of FIG. 11 performs the following intra-frame decoding operations. The static mesh decoder (612) decodes the mesh sub-stream to generate a reconstructed quantized base mesh, and the inverse quantizer (620) applies the quantization parameters of the quantizer inversely to generate the reconstructed base mesh. The video decoder (613) decodes the displacement sub-stream, the image unpacking unit (614) unpacks the images of the decoded displacement video, and the inverse quantizer (615) inversely quantizes the quantized images. The inverse linear lifting unit (616) applies a lifting transform in the reverse process of the encoder to generate the reconstructed displacement. The mesh restoration unit (630) generates a reconstructed deformed mesh based on the reconstructed base mesh and the reconstructed displacement. The video decoder (617) decodes the attribute map sub-stream, and the color conversion unit (640) converts the color format and / or space of the decoded attribute map to generate a decoded attribute map.

[0164] Figure 12 illustrates the inter-frame decoding (or inter-decoding) process of V-Mesh technology.

[0165] Fig. 12 illustrates the configuration and operation of the mesh video decoder (113) of the receiving device of Fig. 1. In addition, Fig. 12 can restore mesh data by performing the reverse process of the inter-frame encoding process of Fig. 7. Each component for the inter-frame decoding process of Fig. 12 corresponds to hardware, software, and / or a combination thereof.

[0166] First, the bitstream received and input to the demultiplexer (711) of the intra frame decoding unit (710) can be separated into a motion sub-stream (also called a motion sub-stream or motion vector sub-stream), a displacement sub-stream, an attribute map sub-stream, and a sub-stream including patch information of a mesh such as V3C / V-PCC.

[0167] According to embodiments, a motion sub-stream may be input to a motion decoder (712) and decoded, a displacement sub-stream may be input to a video decoder (713) and decoded, and an attribute map sub-stream may be input to a video decoder (717) and decoded.

[0168] According to embodiments, a motion sub-stream is decoded through entropy decoding and inverse prediction processes in a motion decoder (712) and restored into motion information (or motion vector information). A base mesh restoration unit (718) combines the restored motion information with a reference base mesh that has already been restored and stored to generate a reconstructed quantized base mesh for the current frame. An inverse quantizer (720) applies inverse quantization to the restored quantized base mesh to generate a reconstructed base mesh. A video decoder (713) decodes a displacement sub-stream, an image unpacking unit (714) unpacks an image of the decoded displacement video, and an inverse quantizer (715) inversely quantizes a quantized image. The reverse linear lifting unit (716) applies a lifting transformation in the reverse process of the encoder to generate a restored displacement. The mesh restoration unit (730) generates a reconstructed deformed mesh, i.e., a final decoded mesh, based on the restored base mesh and the restored displacement.

[0169] According to embodiments, the video decoder (717) decodes the attribute map sub-stream in the same manner as intra decoding, and the color conversion unit (740) converts the color format and / or space of the decoded attribute map to generate a decoded attribute map. The decoded mesh and the decoded attribute map can be utilized by the receiver as final mesh data that can be utilized by the user.

[0170] Referring to Fig. 12, the bitstream includes motion information (also called motion vectors), displacement, and an attribute map. Since Fig. 12 performs inter-frame decoding, it further includes a process of decoding inter-frame motion information. The motion information is decoded, and a restored quantized base mesh for the motion information is generated based on the reference base mesh, thereby generating a restored base mesh. For a description of the operation of Fig. 12, which is identical to that of Fig. 11, refer to the description of Fig. 11.

[0171] Fig. 13 illustrates a mesh data transmission device according to embodiments.

[0172] FIG. 13 corresponds to the transmitting device (100) or mesh video encoder (102) of FIG. 1, the encoder (preprocessor and encoder) of FIG. 2, FIG. 6, or FIG. 7, and / or a transmitting encoding device corresponding thereto. Each component of FIG. 13 corresponds to hardware, software, a processor, and / or a combination thereof.

[0173] The operation process of a transmitter for compressing and transmitting dynamic mesh data using V-Mesh compression technology may be as shown in Fig. 13. The transmitter of Fig. 13 may perform an intra-frame encoding (or intra-encoding or intra-screen encoding) process and / or an inter-frame encoding (or inter-encoding or inter-screen encoding) process.

[0174] The pre-processor (811) receives the original mesh as input and generates a simplified mesh (decimated mesh) (or base mesh) and a fitted decimated mesh (or subdivision). Simplification can be performed based on the target number of vertices or target number of polygons that constitute the mesh. Parameterization, which generates texture coordinates and texture connection information per vertex, can be performed on the simplified mesh. For example, parameterization is a process of mapping a 3D surface to a texture domain for the decimated mesh. If parameterization is performed using the UVAtlas tool, mapping information is generated that can identify where each vertex of the decimated mesh can be mapped on a 2D image. The mapping information is expressed and stored as texture coordinates, and the final base mesh is generated through this process. In addition, the work of quantizing the mesh information in floating-point form into fixed-point form can be performed. This result can be output as a base mesh to a motion vector encoder (813) or a static mesh encoder (814) through a switching unit (812). The pre-processor (811) can perform mesh subdivision on the base mesh to generate additional vertices. Depending on the subdivision method, vertex connection information, texture coordinates, and texture coordinate connection information including the added vertices can be generated. The pre-processor (811) can generate a fitted subdivided mesh by adjusting the vertex positions so that the subdivided mesh becomes similar to the original mesh.

[0175] According to embodiments, the base mesh is output to a motion vector encoder (813) via a switching unit (812) when performing inter-encoding for the corresponding mesh frame, and is output to a static mesh encoder (814) via a switching unit (812) when performing intra-encoding for the corresponding mesh frame. The motion vector encoder (813) may be referred to as a motion encoder.

[0176] For example, when performing intra-encoding (or intra-frame encoding) on ​​the corresponding mesh frame, the base mesh can be compressed through a static mesh encoder (814). In this case, encoding can be performed on connection information, vertex geometry information, vertex texture information, normal information, etc. of the base mesh. The base mesh bitstream generated through encoding is transmitted to a multiplexer (823).

[0177] As another example, when performing inter-encoding (or inter-frame encoding) for the corresponding mesh frame, the motion vector encoder (813) can receive a base mesh and a reference reconstructed base mesh (or a reconstructed quantized reference base mesh) as input, calculate a motion vector between the two meshes, and encode the value. In addition, the motion vector encoder (813) can perform prediction based on connection information using a previously encoded / decoded motion vector as a predictor, and encode a residual motion vector obtained by subtracting the predicted motion vector from the current motion vector. The motion vector bitstream generated through encoding is transmitted to the multiplexer (823).

[0178] The base mesh restoration unit (815) can receive the base mesh encoded by the static mesh encoder (814) or the motion vector encoded by the motion vector encoder (813) and generate a reconstructed base mesh. For example, the base mesh restoration unit (815) can perform static mesh decoding on the base mesh encoded by the static mesh encoder (814) to restore the base mesh. At this time, quantization can be applied before the static mesh decoding, and inverse quantization can be applied after the static mesh decoding. As another example, the base mesh restoration unit (815) can restore 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 calculation unit (816) and the mesh restoration unit (820).

[0179] The displacement calculation unit (816) can perform mesh refinement on the restored base mesh. The displacement calculation unit (816) can calculate a displacement vector, which is a difference value between the vertex positions of the restored base mesh and the fitted subdivision (or refined) mesh generated by the pre-processor (811). At this time, the displacement vector can be calculated as many times as the number of vertices of the refined mesh. The displacement calculation unit (816) can convert the displacement vector calculated in the 3D Cartesian coordinate system into a local coordinate system based on the normal vector of each vertex.

[0180] The displacement vector video generation unit (817) may include a linear lifting unit, a quantizer, and an image packing unit. That is, in the displacement vector video generation unit (817), the linear lifting unit may transform the displacement vector for effective encoding. The transformation may be performed by a lifting transformation, a wavelet transformation, etc., according to embodiments. In addition, quantization may be performed in a quantizer on the transformed displacement vector value, i.e., the transform coefficient. At this time, a different quantization parameter may be applied to each axis of the transform coefficient, and the quantization parameter may be derived according to an encoder / decoder agreement. The transformed and quantized displacement vector information may be packed into a 2D image in the image packing unit. The displacement vector video generation unit (817) may generate a displacement vector video by bundling packed 2D images for each frame, and the displacement vector video may be generated for each GoF (Group of Frame) unit of the input mesh.

[0181] The displacement vector video encoder (818) can encode the generated displacement vector video using a video compression codec. The generated displacement vector video bitstream is transmitted to a multiplexer (823).

[0182] The displacement vector restoration unit (819) may include a video decoder, an image unpacking unit, an inverse quantizer, and an inverse linear lifting unit. That is, the displacement vector restoration unit (819) performs decoding on an encoded displacement vector in the video decoder, performs image unpacking in the image unpacking unit, performs inverse quantization in the inverse quantizer, and then performs inverse transformation in the inverse linear lifting unit to restore the displacement vector. The restored displacement vector is output to the mesh restoration unit (820). The mesh restoration unit (820) restores a deformed mesh based on the base mesh restored by the base mesh restoration unit (815) and the displacement vector restored by the displacement vector restoration unit (819). The restored mesh (or referred to as a restored deformed mesh) has restored vertices, connection information between vertices, texture coordinates, and connection information between texture coordinates.

[0183] The texture map video generation unit (821) can regenerate a texture map based on the texture map (or attribute map) of the original mesh and the restored deformed mesh output from the mesh restoration unit (820). According to embodiments, the texture map video generation unit (821) can assign color information per vertex of the texture map of the original mesh to the texture coordinates of the restored deformed mesh. According to embodiments, the texture map video generation unit (821) can generate a texture map video by grouping the regenerated texture maps by GoF unit for each frame.

[0184] The generated texture map video can be encoded using a video compression codec of the texture map video encoder (822). The texture map video bitstream generated through encoding is transmitted to a multiplexer (823).

[0185] A multiplexer (823) multiplexes a motion vector bitstream (e.g., in case of inter encoding), a base mesh bitstream (e.g., in case of intra encoding), a displacement vector bitstream, and a texture map bitstream into a single bitstream. The single bitstream can be transmitted to a receiver via a transmitter (824). Alternatively, the motion vector bitstream, the base mesh bitstream, the displacement vector bitstream, and the texture map bitstream can be generated as a file with one or more track data or encapsulated into segments and transmitted to a receiver via the transmitter (824).

[0186] Referring to FIG. 13, a transmitting device (encoder) can encode a mesh in an intra-frame or inter-frame manner. A transmitting device according to intra-encoding can generate a base mesh, a displacement vector (or referred to as displacement), and a texture map (or referred to as attribute map). A transmitting device according to inter-encoding can generate a motion vector (or referred to as motion), a displacement vector (or referred to as displacement), and a texture map (or referred to as attribute map). The texture map obtained from the data input unit is generated and encoded based on the restored mesh. Displacement is generated and encoded through the difference in vertex positions between the base mesh and the divided (or subdivided or subdivided) mesh. More specifically, the displacement is the difference in position between the fitted sub-divided mesh and the sub-divided restored base mesh, i.e., the difference in vertex positions between the two meshes. In addition, the base mesh is generated by simplifying and encoding the original mesh through pre-processing. Motion is generated as motion vectors for the mesh of the current frame based on the reference base mesh of the previous frame.

[0187] Fig. 14 illustrates a mesh data receiving device according to embodiments.

[0188] Fig. 14 corresponds to the receiving device (110) or mesh video decoder (113) of Fig. 1, the decoder of Fig. 11 or Fig. 12, and / or the receiving decoding device corresponding thereto. Each component of Fig. 14 corresponds to hardware, software, a processor, and / or a combination thereof. The receiving (decoding) operation of Fig. 14 may follow the reverse process of the corresponding process of the transmitting (encoding) operation of Fig. 13.

[0189] The bitstream of the mesh data received by the receiver (910) is demultiplexed into a compressed motion vector bitstream (e.g., inter decoding) or a base mesh bitstream (e.g., intra decoding), a displacement vector bitstream, and a texture map bitstream after file / segment decapsulation in the demultiplexer (911). For example, if the current mesh has inter-screen encoding (i.e., inter encoding) applied, the motion vector bitstream is received, demultiplexed, and then output to the motion vector decoder (913) via the switching unit (912). As another example, if the current mesh has intra-screen encoding (i.e., intra encoding) applied, the base mesh bitstream is received, demultiplexed, and then output to the static mesh decoder (914) via the switching unit (912). Here, the motion vector decoder (913) may be referred to as a motion decoder.

[0190] According to embodiments, if the current mesh has inter-screen encoding applied according to frame header information, the motion vector decoder (913) can perform decoding on the motion vector bitstream. According to embodiments, the motion vector decoder (913) can reconstruct the final motion vector by adding the previously decoded motion vector as a predictor to the residual motion vector decoded from the bitstream.

[0191] According to embodiments, if the current mesh has been subjected to in-screen encoding according to frame header information, the static mesh decoder (914) can decode the base mesh bitstream to restore connection information, vertex geometry information, texture coordinates, normal information, etc. of the base mesh.

[0192] According to embodiments, the base mesh restoration unit (915) can restore the current base mesh based on the decoded motion vector or the decoded base mesh. For example, if the current mesh has inter-screen encoding applied, the base mesh restoration unit (915) can generate a restored base mesh by adding the decoded motion vector to the reference base mesh and then performing inverse quantization. As another example, if the current mesh has intra-screen encoding applied, the base mesh restoration unit (915) can generate a restored base mesh by performing inverse quantization on the base mesh decoded through the static mesh decoder (914).

[0193] According to embodiments, the displacement vector video decoder (917) can decode the displacement vector bitstream as a video bitstream using a video codec.

[0194] According to embodiments, the displacement vector restoration unit (918) extracts displacement vector transform coefficients from the decoded displacement vector video, and restores the displacement vector by applying inverse quantization and inverse transformation processes to the extracted displacement vector transform coefficients. To this end, the displacement vector restoration unit (918) may include an image unpacking unit, an inverse quantizer, and an inverse linear lifting unit. If the restored displacement vector is a value in a local coordinate system, a process of inversely transforming it into a Cartesian coordinate system may be performed.

[0195] The mesh restoration unit (916) can generate additional vertices by performing subdivision on the restored base mesh. Through subdivision, vertex connection information including the added vertices, texture coordinates, and texture coordinate connection information can be generated. At this time, the mesh restoration unit (916) can generate a final restored mesh (or a restored deformed mesh) by combining the subdivided restored base mesh with the restored displacement vector.

[0196] According to embodiments, the texture map video decoder (919) can decode the texture map bitstream as a video bitstream using a video codec to restore the texture map. The restored texture map has color information for each vertex contained in the restored mesh, and the color value of each vertex can be obtained from the texture map using the texture coordinates of each vertex.

[0197] According to embodiments, the mesh restored by the mesh restoration unit (916) and the texture map restored by the texture map video decoder (919) are shown to the user through a rendering process in the mesh data renderer (920).

[0198] Referring to FIG. 14, a receiving device (decoder) can decode a mesh in an intra-frame or inter-frame manner. A receiving device according to intra-decoding can receive a base mesh, a displacement vector (or referred to as displacement), a texture map (or referred to as attribute map), and render mesh data based on the restored mesh and the restored texture map. A receiving device according to inter-decoding can receive a motion vector (or referred to as motion), a displacement vector (or referred to as displacement), a texture map (or referred to as attribute map), and render mesh data based on the restored mesh and the restored texture map.

[0199] A mesh data transmission device and method according to embodiments may pre-process mesh data, encode the pre-processed mesh data, and transmit a bitstream including the encoded mesh data. A point mesh data reception device and method according to embodiments may receive a bitstream including mesh data and decode the mesh data. The mesh data transmission and reception method / device according to embodiments may be abbreviated as method / device according to embodiments. The mesh data transmission and reception method / device according to embodiments may also be referred to as 3D data transmission and reception method / device or point cloud data transmission and reception method / device.

[0200] As described above, the V-Mesh method can encode displacement information generated during the encoding process using a video codec-based encoder. In this case, the displacement information can be packed into a 2D image (or frame) and then encoded using a 2D video codec (i.e., a video compression codec). In the present disclosure, the displacement information can be referred to as a displacement vector, a displacement vector transform coefficient, or displacement data.

[0201] Meanwhile, the present disclosure can pack a texture map and a displacement information frame into a single frame and then encode them using a video codec (i.e., a video compression codec). This allows the video codec used for conventional displacement information compression and the video codec used for texture map compression to be combined into one, thereby increasing coding efficiency. For example, assuming that a video codec (e.g., HEVC or SHVC or VVC) is used for displacement information representing geometry information, and another video codec (e.g., HEVC or SHVC or VVC) is used for a texture map, packing the texture map and displacement information into a single frame allows one video codec to be used instead of two. Here, HEVC supports encoding / decoding of a single layer, and SHVC, as an extension of HEVC, supports encoding / decoding of multiple layers (i.e., one base layer and one or more enhancement layers). Additionally, VVC is a successor standard to SHVC and supports encoding / decoding of multiple layers (i.e., multilayers).

[0202] In the present disclosure, packed data in which a texture map and displacement information are packed into a single frame is referred to as Packed Video Data (PVD) or a PVD bitstream. In addition, a frame in which a texture map and a displacement information frame are packed together is referred to as a 'packed video frame or texture map and displacement information frame' or a 'texture map and displacement vector frame'. In addition, in the present disclosure, a texture map may be referred to as texture map data, texture data, attribute data, attribute information, or attribute map. In addition, displacement information may be referred to as geometry data.

[0203] The present disclosure may apply scalable coding to texture maps and / or displacement information. If scalable coding is applied to both the texture map and displacement information, the resolution of the texture map and the resolution of the displacement information may be the same or different. Furthermore, when packing the texture map and displacement information with scalable coding into a single frame, the resolutions of the texture map and displacement information packed into a single frame may be the same or different.

[0204] The present disclosure proposes a method for defining signaling (e.g., High Level Syntax, hereinafter referred to as HLS) related to scalable coding of dynamic mesh data. In addition, the present disclosure proposes signaling (HLS) related to a method for packing displacement data and texture data (or texture map data) into a single frame (packed video). In this way, the present disclosure proposes a scalable coding method for dynamic mesh data, and in particular, a method for defining scalable coding HLS for an integrated packing method of displacement data (or referred to as geometry data) and texture data (or referred to as texture map data or attribute data).

[0205] That is, a dynamic mesh content receiver may be required to decode / render dynamic mesh content in various configurations depending on resources such as memory, decoder performance, display, or producer's intention, and the content producer may encode dynamic mesh content by applying scalable coding (i.e., scalability) according to pre-defined and / or newly defined standards such as Level of Detail (hereinafter referred to as LoD) taking these factors into consideration.

[0206] At this time, since the dynamic mesh content receiver must decode each data included in the dynamic mesh content to know whether scalable coding is applied or not, a dynamic mesh content receiver with restrictions related to scalable coding may experience unnecessary or abnormal operation and inefficient resource management.

[0207] To solve this, the present disclosure defines a syntax capable of signaling scalable encoded information by integrating and packing (packed video) geometry data and texture data among the data constituting dynamic mesh content into a single frame. In the present disclosure, data of the PVD (Packed Video Data) type among the data constituting the dynamic mesh means data configured by packing a displacement frame and a texture map, which are among the geometry data (or referred to as geometry information), into a single frame, and the present disclosure proposes HLS to support PVD-based scalability functions.

[0208] That is, the present disclosure can integrate displacement information and attribute information (texture map) and pack them into a single video frame. For example, by packing displacement information into a video frame and attribute information into the remaining area, two types of data can be jointly packed into a single frame. The decoder of the receiving device according to the embodiments has the effect of unpacking data packed into a single frame to simultaneously decode displacement information and / or attribute information of related areas.

[0209] Hereinafter, the present disclosure will describe in detail the scalable coded geometry data type, codec ID signaling for scalable coding, scalable coding general information signaling, etc.

[0210] The V-DMC referred to in this disclosure may also be referred to as V-Mesh, and the terms are used with the same meaning. Dynamic mesh data refers to a type of mesh data, which is a form of point cloud data, and refers to mesh data in which objects and / or people corresponding to objects change over time, i.e., have movement.

[0211] FIG. 15 is a diagram showing an example of a dynamic mesh bitstream structure encoded and transmitted by a transmitting device of the present disclosure. That is, dynamic mesh content can be encoded with a bitstream structure as in FIG. 15 and transmitted to a receiving device. In particular, the present disclosure can use a sample stream data unit used when encoding V3C content of the V3C codec specification (ISO / IEC 23090-5) as in FIG. 15. The present disclosure relates to a method for applying scalable coding to geometry and texture data packed in one frame when the V3C content format is PVD.

[0212] That is, a bitstream (called a V-DMC bitstream or a dynamic mesh bitstream) transmitted from a transmitting device to a receiving device of the present disclosure may be composed of a sample stream DMC header and a plurality of sample stream DMC units. In the present disclosure, the sample stream DMC header may be referred to as a sample stream header, and the sample stream DMC unit may be referred to as a sample stream data unit.

[0213] At this time, if the sample stream DMC unit follows the V3C codec specification (ISO / IEC 23090-5), the sample stream DMC unit can be composed of V3C sample stream size information and a V3C unit. The V3C unit is again composed of a V3C unit header (V3C_unit_header) and a V3C unit payload (V3C_unit_payload).

[0214] The above V3C sample stream size information specifies the size of the subsequent V3C unit in bytes.

[0215] The above V3C unit header includes type information (vuh_unit_type) indicating the type of data carried by the corresponding V3C unit payload. The above V3C unit payload can carry one of a V3C / V-DMC parameter set (VPC), Atlas Data (AD), Base Mesh Data (BMD), Displacement Data / Geometry Video Data (DD / GVD), Attribute Video Data (AVD), and Packing Video Data (PVD) according to the type information (vuh_unit_type).

[0216] Here, VPS may include parameter set information such as decoder configuration information related to mesh encoding / decoding and sequence header. Atlas data (AD) may include additional information such as 2D mapping or texture mapping for 3D objects. Base mesh data (BMD) is compressed base mesh data for mesh encoding / decoding. In addition, DD / GVD represents displacement data (or displacement information), where DD represents displacement data that is arithmetic coded and GVD represents displacement data that is encoded using a video codec. Attribute video data (AVD) is attribute or texture data (or texture map information) compressed using a video codec. Packed video data (PVD) is packed texture map and displacement information compressed using a video codec.

[0217] Fig. 16 is a diagram showing an example of the syntax structure of a V3C unit payload (V3C_unit_payload) according to embodiments. In Fig. 16, numBytesInV3CPayload indicates the size of the corresponding V3C unit, which can be specified by the V3C sample stream size information.

[0218] For example, if the type information (vuh_unit_type) of the above V3C unit header indicates V3C_VPS, the corresponding V3C unit payload includes a V3C parameter set (v3c_parameter_set()) that includes overall encoding information of the bitstream, and if it indicates V3C_AD, it includes an atlas sub bitstream (atlas_sub_bitstream()) that carries atlas data.

[0219] And, if the type information (vuh_unit_type) of the V3C unit header indicates PVD, the V3C unit payload includes a packed video sub-bitstream (video_sub_bitstream()) carrying packed video data. That is, in the present disclosure, scalable coded packet video data (i.e., texture and displacement data packed into one frame) is transmitted to a receiving device through a V3C unit corresponding to V3C_PVD (vuh_unit_type == V3C_PVD). At this time, the V3C unit payload of the scalable coded packed video data uses the video_sub_bitstream format, which has a NAL unit structure coded with HEVC or VVC (SHVC or multi-layer VVC).

[0220] FIG. 17 is a diagram showing another example of a transmitter according to embodiments. The transmitter of FIG. 17 may correspond to the transmitter of FIG. 1, the transmitter of FIG. 6, the transmitter of FIG. 7, or the transmitter of FIG. 13. Therefore, parts not described in FIG. 17 will refer to the description of the transmitter of FIG. 1, the transmitter of FIG. 6, the transmitter of FIG. 7, or the transmitter of FIG. 13. The elements of the transmitter illustrated in FIG. 17 may be implemented by hardware, software, a processor connected to a memory, and / or a combination thereof. That is, the elements of the transmitter of FIG. 17 may be implemented by hardware, software, firmware, or a combination thereof, including one or more processors or integrated circuits configured to communicate with one or more memories, although not illustrated in the drawing. One or more processors may perform at least one or more of the operations and / or functions of the elements of the transmitter of FIG. 17 described above. Additionally, one or more processors may operate or execute a set of software programs and / or instructions for performing operations and / or functions of elements of the transmitting device of FIG. 17.

[0221] In Fig. 17, the pre-processing unit can simplify the original mesh data to generate a base mesh. For a detailed description of the pre-processing unit, refer to the pre-processing description of Fig. 2, Fig. 3, Fig. 6, Fig. 7, or Fig. 13, and a detailed description is omitted here.

[0222] And, in case of inter-frame, the motion encoder (or motion vector encoder) calculates a motion vector based on the previous reference restoration base mesh and the base mesh and encodes the calculated motion vector, and in case of intra-frame, the base mesh is encoded through the base mesh encoder (or static mesh encoder) and outputs the base mesh bitstream. For example, the motion encoder can generate a base mesh bitstream by performing a prediction on the base mesh based on the mesh in the reference frame for the current frame and generating and encoding the residual. In addition, the motion of the current base mesh can be compensated by estimating the motion vector of the mesh between the current frame and the reference frame.

[0223] In the present disclosure, a displacement calculation unit (also referred to as a displacement vector calculation unit) (11020) can calculate a displacement vector in units of levels or LoD. The present disclosure calculates a displacement vector in units of levels, as one embodiment. In the present disclosure, a level may be referred to as a subdivision level or LoD level.

[0224] In the present disclosure, levels and LoD can be defined during the subdivision process of the base mesh. In one embodiment, the subdivision of the base mesh is performed in a mesh subdivision unit (not shown). Furthermore, in one embodiment, the mesh subdivision unit is included in the preprocessor of FIG. 2, FIG. 3, FIG. 6, FIG. 7, FIG. 13, or FIG. 17.

[0225] More specifically, in the mesh refinement unit, mesh refinement can be performed n times by user parameters or a promise of the encoder (i.e., transmitting device) / decoder (i.e., receiving device). According to embodiments, the vertices of the base mesh are vertices of level 0 (R0), the vertices newly generated by performing the refinement once are vertices of level 1 (R1), … the vertices newly generated by performing the refinement n times are vertices of level n (R n) can be defined as vertices of level 0 (R0). For convenience of explanation, the present disclosure refers to vertices of level 0 (R0) as level 0 vertices, vertices of level 1 (R1) as level 1 vertices, …, level n (R n ) can be called level n vertices. Also, level 0 is called the 0th level (R0), level 1 is called the 1st level (R1), … level n is called the nth level (R n ) can be called.

[0226] According to embodiments, LoD0, LoD1, … LoDn can be defined as in the following mathematical expression 1.

[0227] [Mathematical Formula 1]

[0228] LoD0 = R0

[0229] LoD1 = R0+ R1= LoD0 + R1

[0230] …

[0231] LoDn = R0+ R1+, … + R n = LoDn-1 + R n

[0232] That is, the base mesh includes vertices for LoD0. And, the first subdivision mesh generated by subdividing the base mesh once includes vertices for LoD1. That is, LoD1 includes vertices of the base mesh (i.e., R0 vertices) and vertices of a newly generated level 1 by subdividing the base mesh (i.e., R1 vertices). In addition, the second subdivision mesh generated by subdividing the first subdivision mesh again includes vertices for LoD2. That is, LoD2 includes vertices of the base mesh (i.e., R0 vertices), vertices of a newly generated level 1 by subdividing the base mesh (i.e., R1 vertices), and vertices of a newly generated level 2 by subdividing the first subdivision mesh (i.e., R2 vertices).

[0233] In this way, LoD represents the level of detail of mesh data content, and as the LoD (or level) index increases, the distance between vertices becomes closer and the level of detail increases. In other words, the smaller the LoD value, the lower the detail of the mesh data content, and the larger the LoD value, the higher the detail of the mesh data content.

[0234] According to embodiments, the displacement calculation unit (11020) may calculate a displacement vector (i.e., position information of a vertex in the base mesh) for each level or each LoD. For example, if the displacement vector is calculated for each level, for level 0 (R0), the displacement vector may be calculated as many times as the number of vertices in the base mesh. In addition, for level 1 (R1), the displacement vector may be calculated as many times as the number of newly created vertices in the first subdivision mesh, and for level 2 (R2), the displacement vector may be calculated as many times as the number of newly created vertices in the second subdivision mesh. The same applies to other levels. In the present disclosure, the displacement information (or displacement data) may be a displacement vector indicating position information.

[0235] For convenience of explanation, the present disclosure disp the displacement vector or displacement vector transform coefficients of level 0 (R0). R0 , and the displacement vector or displacement vector transformation coefficients of level 1 (R1) are disp R1 , and the displacement vector or displacement vector transformation coefficients of level 2 (R2) are disp R2 In the present disclosure, the displacement vector conversion coefficient may be used interchangeably with the conversion coefficient with the same meaning.

[0236] According to embodiments, the displacement packing unit (11021) can pack displacement vectors or displacement vector transformation coefficients into one image (i.e., one frame) for each subdivision level (R). That is, the number of subdivision levels (disp R0 -disp RN) as many images (i.e. frames) as there are (disp R0 frame - disp RN A frame) is generated. According to embodiments, the displacement packing unit (11021) may pack displacement data (i.e., displacement vector or displacement vector transform coefficients) into a video frame in the reverse direction of the image (i.e., writing the first data from the end point of the image and packing in reverse order) or in the forward direction of the image (i.e., writing the first data from the beginning point of the image and packing in reverse order). In the present disclosure, signaling information (e.g., displacement_Reverse_Packing_flag) indicates whether the displacement data is packed into a video frame in the reverse direction of the image (i.e., writing the first data from the end point of the image and packing in reverse order) or in the forward direction of the image (i.e., writing the first data from the beginning point of the image and packing in reverse order).

[0237] The present disclosure refers to the displacement vector or displacement vector transform coefficients of level 0 (R0) as the displacement vector or displacement vector transform coefficients of the base layer, and the remaining levels (R1-R N ) are referred to as displacement vectors or displacement vector transform coefficients of the enhancement layer. In the present disclosure, the base layer may be referred to as a first layer, and one or more enhancement layers may be referred to as one or more second layers.

[0238] According to embodiments, the displacement vector encoder (11022) may encode displacement vectors or displacement vector transform coefficients of each frame through a video codec in units of levels (i.e., layers). At this time, each layer may include displacement vectors or displacement vector transform coefficients corresponding to one LoD, or each layer may include displacement vectors or displacement vector transform coefficients corresponding to multiple LoDs. The present disclosure may identify how geometry data (displacement vectors or displacement vector transform coefficients) are mapped to each layer of scalably coded packed video based on single_lod_displacement_flag. Here, the displacement vector encoder (11022) may be a Scalable High Efficiency Video Coding (SHVC) encoder or another encoder capable of scalable coding.

[0239] According to embodiments, the displacement vector restoration unit (11023) can restore the displacement vector in units of levels (i.e., layer units) by performing the reverse process of the displacement vector encoding on the displacement vector or displacement vector transformation coefficient encoded in the displacement vector encoder (11022) in units of levels (i.e., layer units). That is, the displacement vector restoration unit (11023) can perform displacement vector depacking depending on the method of encoding the displacement vector, for example, when encoding is based on a video codec. If encoding is performed through an SHVC encoder in the displacement vector encoder (11022), the displacement vector restoration unit (11023) can also perform displacement vector restoration through an SHVC decoder.

[0240] According to embodiments, the geometry reconstruction unit (11024) reconstructs full-resolution geometry based on the base mesh and the restored displacement vectors of each level (i.e., layer). In the present disclosure, the reconstructed geometry may be referred to as a restored mesh. That is, the geometry reconstruction unit (11024) may restore positional information of vertices.

[0241] According to embodiments, a texture transfer unit (or texture map generation unit) (11025) can regenerate a texture map of a current mesh based on an input mesh (i.e., a texture map (or attribute map) of an original mesh) and a mesh restored by a geometry reconstruction unit (11024) (i.e., full resolution geometry).

[0242] According to embodiments, the multi-resolution texture map generation unit (11026) can perform down sampling on the regenerated texture map to generate a multi-resolution texture map.

[0243] According to embodiments, the multi-resolution texture map generation unit (11026) may perform down-sampling independently of the level (R) of the displacement vector, or may perform down-sampling corresponding to the level (R) of the displacement vector. That is, the multi-resolution texture map generation unit (11026) may perform down-sampling on a full resolution texture map to generate a texture map for each LoD (or each LoD level). For example, a base mesh may be LoD0, and a mesh obtained by applying mesh subdivision n times to the base mesh may be LoD n When defined as a mesh, the multi-resolution texture map generation unit (11026) can perform downsampling n times to generate a texture map for each LoD (or each LoD level).

[0244] According to embodiments, the integrated packing unit (11027) may pack the texture map for each LOD level (or each LoD) output from the multi-resolution texture map generation unit (11026) into a frame in which the displacement information for each LOD level (or each LoD) output from the displacement packing unit (11021) is packed. In this case, as an embodiment, the texture map is packed at the top of the frame, and the displacement information is packed at the bottom. That is, the displacement information for each LoD level in the displacement packing unit (11021) may be packed at the bottom of the corresponding frame.

[0245] According to embodiments, a layer (LoD or LoD level) of a texture map packed in the integrated packing unit (11027) may be packed into a frame in which displacement information of the same layer (LoD or LoD level) is packed. For example, a displacement vector of a base layer may be packed into a frame (i.e., disp R0 ) (W frame) through downsampling τex / 2 N )x((H τex / 2 N) is packed as shown in the picture in the center right of FIG. 17. The present disclosure stipulates that the texture map and the displacement information are packed with the same width as an embodiment. That is, the height of the frame into which the texture map is packed and the height of the frame into which the displacement information is packed may be different depending on the amount of data of the texture map and the displacement information, but the width of the frame into which the texture map is packed and the width of the frame into which the displacement information is packed are the same. That is, the texture map and the displacement information are each packed into the frame in the form of a rectangle having the same width. Therefore, when the amount of data to be packed is smaller than the area of ​​the corresponding rectangle, padding may be performed to fit the rectangular area. In the packed video frame in the picture in the center right of FIG. 17, padding (11032) is performed to fit a portion of the rectangle into which the displacement information (11031) is packed to the corresponding rectangular area. The present disclosure stipulates that the same rule is applied to other layers as an embodiment. According to embodiments, the location of displacement information within a packed video frame can be identified based on one or more of displacement_region_top_left_x, displacement_region_top_left_y, displacement_region_width_minus1, and displacement_region_height_minus1. displacement_region_top_left_x and displacement_region_top_left_y represent the upper left coordinates of the region where the displacement data is located within the packed video frame. displacement_region_width_minus1 and displacement_region_height_minus1 represent the horizontal / vertical lengths of the region where the displacement data is located within the packed video frame.

[0246] According to embodiments, the integrated encoder (11028) performs video codec-based scalable encoding on the output of the integrated packing unit (11027). That is, data (texture map and displacement information) of a frame packed for each layer can be encoded using each independent video codec. For example, if the number of layers including the base layer is 4, data of a packed video frame of the corresponding layer (LoD or LoD level) can be encoded using 4 independent video codecs. Here, the integrated encoder (11028) may be an SHVC encoder or another encoder capable of scalable coding.

[0247] Through this process, a texture map and displacement information bitstream (called a PVD bitstream) is generated for each layer. That is, the scalable texture & displacement bitstream can include the texture map and displacement information bitstream of the base layer ~ the base layer texture map and displacement information bitstream of the enhancement layer N.

[0248] According to embodiments, a multiplexer (not shown) may multiplex an input base mesh bitstream and a scalable texture & displacement bitstream (or referred to as a PVD bitstream) into a single bitstream as shown in FIG. 15 and then transmit the multiplexer to a receiving device. Alternatively, the base mesh bitstream and the scalable texture & displacement bitstream (or referred to as a PVD bitstream) may be encapsulated into a file / segment and transmitted to the receiving device. According to embodiments, the bitstream multiplexed in the multiplexer may be transmitted via a network or stored in a digital storage medium. Here, the network may include a broadcasting network and / or a communication network, and the digital storage medium may include various storage media such as a USB, SD, CD, DVD, Blu-ray, HDD, and SSD.

[0249] FIG. 18 is a diagram showing another example of a receiving device according to embodiments. The receiving device of FIG. 18 may correspond to the receiving device of FIG. 1, the receiving device of FIG. 11, the receiving device of FIG. 12, or the receiving device of FIG. 14. Therefore, parts not described in FIG. 18 will refer to the description of the receiving device of FIG. 1, the receiving device of FIG. 11, the receiving device of FIG. 12, or the receiving device of FIG. 14. The elements of the receiving device illustrated in FIG. 18 may be implemented by hardware, software, a processor connected to a memory, and / or a combination thereof. That is, the elements of the receiving device of FIG. 18 may be implemented by hardware, software, firmware, or a combination thereof, including one or more processors or integrated circuits configured to communicate with one or more memories, although not illustrated in the drawing. One or more processors may perform at least one or more of the operations and / or functions of the elements of the receiving device of FIG. 18 described above. Additionally, one or more processors may operate or execute a set of software programs and / or instructions for performing operations and / or functions of elements of the receiving device of FIG. 18.

[0250] In particular, FIG. 18 is an example of performing scalable decoding and restoring the texture map and displacement information by separating them (split) from the frame of a specific layer (i.e., the target layer) when the texture map and displacement information are packed into one frame for each layer as in FIG. 17 and encoding based on a video codec is performed and transmitted for each layer.

[0251] According to embodiments, a bitstream of mesh data received by a receiver (not shown) may be demultiplexed into a base mesh bitstream and a scalable texture & displacement bitstream (or PVD bitstream) in a demultiplexer (not shown) after file / segment decapsulation. If the current mesh has inter-screen encoding (i.e., inter-encoding) applied, the base mesh bitstream may be a motion vector bitstream.

[0252] According to embodiments, the base mesh bitstream is provided to a motion decoder (or motion vector decoder) through a switching unit or to a base mesh decoder (or static mesh decoder).

[0253] For example, if the current mesh has inter-screen encoding (i.e., inter encoding) applied, the base mesh bitstream, i.e., the motion vector bitstream, is received, demultiplexed, and then output to the motion decoder through the switching unit. As another example, if the current mesh has intra-screen encoding (i.e., intra encoding) applied, the base mesh bitstream is received, demultiplexed, and then output to the base mesh decoder through the switching unit.

[0254] According to embodiments, the motion decoder may perform decoding on a motion vector bitstream on a vertex-by-vertex basis or a subgroup basis.

[0255] According to embodiments, the motion decoder can reconstruct the final motion vector by adding a differential motion vector (i.e., a residual motion vector) decoded from a bitstream using a previously decoded motion vector as a predictor. That is, the motion decoder can decode a differential motion vector (or a residual motion vector) in units of vertices or subgroups (or subblocks) through a motion vector bitstream, and perform prediction based on connection information using a previously decoded motion vector as a predictor to decode the motion vector by adding it to the residual motion vector.

[0256] According to embodiments, the base mesh decoder can decode the base mesh bitstream to restore connection information, vertex geometry information, texture coordinates (i.e., attribute geometry information), normal information, etc. of the base mesh.

[0257] According to embodiments, the base mesh restoration unit may restore the current base mesh based on the decoded motion vector or the decoded base mesh. For example, if the current mesh has inter-screen encoding applied, the base mesh restoration unit may add the decoded (or restored) motion vector to the reference base mesh and then perform inverse quantization to generate the restored base mesh (i.e., the current base mesh). As another example, if the current mesh has intra-screen encoding applied, the base mesh restoration unit may perform inverse quantization on the base mesh decoded (or restored) through the base mesh decoder to generate the restored base mesh (i.e., the current base mesh).

[0258] According to embodiments, the mesh subdivision unit can generate additional vertices by performing subdivision on the base mesh. The present disclosure can implicitly derive and generate geometric information connection information, texture coordinate connection information, and texture coordinates according to the subdivision method.

[0259] According to embodiments, mesh subdivision in the mesh subdivision unit may be performed n times by user parameters or a promise of the encoder / decoder. According to embodiments, the vertex of the base mesh is R0, the vertex newly generated by performing subdivision 1 is R1, … The vertex generated by performing subdivision n times is R n LOD when defined as n can be defined as in the following mathematical expression 2.

[0260] [Equation 2]

[0261] LOD n = R9 R9 , ..., R n

[0262] In the present disclosure, the base mesh restoration unit and the mesh refinement unit may be configured as separate blocks or modules, or may be configured in the geometry reconstruction unit (15014).

[0263] According to embodiments, the integrated decoder (15011) can perform video codec-based scalable decoding on a demultiplexed scalable texture & displacement bitstream (or PVD bitstream). In the present disclosure, the scalable texture & displacement bitstream can include all or part of a texture map and displacement information bitstream of a base layer to a base layer texture map and displacement information bitstream of an enhancement layer N.

[0264] According to embodiments, the integrated decoder (15011) can decode the texture map and displacement information of each frame through a video codec on a layer-by-layer basis. That is, the texture map and displacement information bitstream of a frame packed and encoded for each layer can be decoded using each independent video codec. For example, if the number of layers including the base layer is 4, the texture map and displacement information bitstream of a frame of the corresponding layer (LoD or LoD level) can be decoded using 4 independent video codecs. Here, the integrated decoder (15011) may be an SHVC decoder or another decoder capable of scalable decoding.

[0265] According to embodiments, the target frame determination unit (15012) can determine a target frame (or target packed video frame) among the frames of each layer scalably decoded by the integrated decoder (15011). The present disclosure can determine the target frame according to the performance of the receiver, the network environment, etc. Here, the target frame may be a frame up to a specific layer, or a frame of a specific layer. In other words, the target frame may be a frame of one or more layers.

[0266] According to embodiments, the segmentation unit (15013) can segment a texture map and displacement information from the target frame determined by the target frame determination unit (15012). The segmented target displacement information is output to the geometry reconstruction unit (15014). If the displacement information is first packed into a frame at the transmitting side and then the texture map is packed into the frame, the target displacement frame including the segmented target displacement information can be output to the geometry reconstruction unit (15014). According to embodiments, the segmentation unit (15013) can separate the texture map and displacement information from the packed video frame based on signaling information (e.g., the scalable packed video coding layer information of FIG. 22). For example, the position of the displacement information can be identified based on displacement_region_top_left_x, displacement_region_top_left_y, displacement_region_width_minus1, and displacement_region_height_minus1. displacement_region_top_left_x, displacement_region_top_left_y represent the upper left coordinates of the region where the displacement data is located within the packed video frame. displacement_region_width_minus1, displacement_region_height_minus1 represent the width / height of the region where the displacement data is located within the packed video frame.

[0267] The geometry reconstruction unit (15014) can perform reverse packing on the target displacement frame, restore the displacement vector, and add a refined restoration base mesh to the restored displacement vector to generate a final restored displacement vector. According to embodiments, the geometry reconstruction unit (15014) can perform reverse packing of the displacement vector based on signaling information (e.g., scalable packed video coding layer information of FIG. 22). For example, displacement_Reverse_Packing_flag indicates whether the displacement data is packed in the reverse direction of the image (i.e., writing the first data from the end point of the image and packing in reverse order) or in the forward direction of the image (i.e., writing the first data from the first point of the image and packing in forward direction) when packed into the video frame. The final restored displacement vector generated through this process is a displacement vector of a specific LoD (or LoD level) determined by the target frame.

[0268] According to embodiments, by applying a texture map of a specific LoD (or LoD level) divided in a split section (15012) to a final generated specific LoD (or LoD level), a final restoration mesh of the LoD (or LoD level) can be constructed.

[0269] According to embodiments, a transmitting side packs and scalably codes texture maps and displacement information of each layer into each frame to generate a scalable texture & displacement bitstream (or PVD bitstream), and a receiving side performs scalable decoding on the scalable texture & displacement bitstream (or PVD bitstream) and then signals information related to packing and scalable coding to segment texture maps and displacement information from a target frame.

[0270] The following describes the settings of a VPS (V3C parameter set) for signaling scalable V-DMC using packed video. This disclosure describes two cases: one is how to signal SHVC or multi-layer VVC in a VPS, and the other is how to set values ​​in packing_information.

[0271] In one embodiment, the present disclosure can perform SHVC or multi-layer VVC signaling in a VPS via the first option or the second option. The present disclosure can basically signal the codec used for scalable V-DMC via the ptl_profile_codec_group_idc field of profile_tier_level() transmitted within the VPS.

[0272] FIG. 19 is a diagram showing an example of codec group profile components according to embodiments. That is, FIG. 19 shows an example of signaling of a scalable coding codec ID.

[0273] The first option is to assign a new ptl_profile_codec_group_idc value as shown in Fig. 19. For example, if the value of ptl_profile_codec_group_idc is 5, the codecgroup indicates HEVC Scalable Main10, and if the value of ptl_profile_codec_group_idc is 6, the codecgroup indicates VVC multi-layer Main10.

[0274] The second option is to set the ptl_profile_codec_group_idc value to 127 and use the component codec mapping SEI message. That is, as shown in FIG. 20, the ccm_codec_id value is assigned (for example, 0xA) and ccm_codec_4cc can be specified as the value of 'shv1' (HEVC Scalable Main10) or 'mvv1' (VVC Multilayer Main10). In this case, the newly defined ccm_codec_4cc value must be registered in the MP4RA according to the method specified in Annex D of ISO / IEC 14496-12. FIG. 20 is a diagram showing an example of the syntax structure of the component codec mapping SEI message according to embodiments. The following is a method of setting values ​​in other packing_information among the settings of VPS for signaling scalable V-DMC using packed video.

[0275] That is, the value is determined as follows for packing_information() included in vps_packed_video_extension of VPC (V3c_parameter_set).

[0276] pin_geometry_present_flag and pin_attribute_present_flag must be set to '1'. This means that the packed video consists of geometry and attributes. Also, the value of pin_attribute_type_id is set to '0' to indicate that the attribute data consists of a texture.

[0277] The following describes a proposed method to signal the scalability information for packed video.

[0278] That is, each layer of packed video can contain a single texture LoD and one or more displacement LoDs. In addition, signaling of how many LoDs of displacement data are contained in each layer is necessary.

[0279] According to embodiments, the present disclosure may signal the number of packed LoDs in SEI messages.

[0280] FIG. 21 is a diagram showing an example of the syntax structure of scalable_packed_video_layer_info (payloadSize) according to embodiments. In the present disclosure, scalable_packed_video_layer_info (payloadSize) may be referred to as scalable coding information.

[0281] When transmitting the information to the receiving device by signaling it as an SEI message according to embodiments, the method for parsing the SEI message in the receiving device is as follows. First, the V3C unit corresponding to V3C_AD is parsed (i.e., the V3C unit having a value of vuh_unit_type==V3C_AD). Next, the nal unit corresponding to NAL_PREFIX_ESEI (or NAL_PREFIX_NSEI) is parsed to parse the SEI message included in the payload to read the information. At this time, the SEI message may have a form as shown in FIG. 21.

[0282] That is, the present disclosure can signal the number of packed LoDs (e.g., num_lod_displacement) through the SEI message (sei_rbsp() of NAL_PREFIX_ESEI or NAL_SUFFIX_ESEI) of the NAL sample stream in the V3C_AD (Atlas Data) atlas sub-bitstream of the V3C sample stream as shown in FIG. 15.

[0283] That is, in Fig. 21, single_lod_displacement_flag is a flag that indicates how geometry (displacement) data is mapped to each layer of scalable coded packed video.

[0284] According to embodiments, the receiving device can infer up to which LoD level (i.e., level) displacement data belonging to each layer is included by using single_lod_displacement_flag. If the value of single_lod_displacement_flag is '1', it indicates that each layer includes displacement data corresponding to one LoD. If the value of single_lod_displacement_flag is '0', additional information is used to determine the number of LoDs of displacement data belonging to each layer.

[0285] num_lod_displacement[j] represents the number of LoDs of displacement data included in the jth layer and is defined as an integer with a minimum value of 1. Based on this information, the receiving device can select a layer to decode according to the target LoD for performing 3D mesh reconstruction.

[0286] According to embodiments, in order for a receiving device to reconstruct a 3D mesh corresponding to a specific resolution (or LoD), the packed video for the corresponding target layer must be decoded, and a task (i.e., a process) of splitting the attribute (i.e., a texture map) and the displacement data from the decoded packed video must be performed. Alternatively, it must be possible to specify which area within the packed video (i.e., a frame) is the attribute and which area is the displacement data. In the case of general non-scalable packed video, the locations of the attribute and displacement data can be specified through the existing pin_information, but in the case of scalable coded packed video, this information is required for each ray. In the case of attribute data, a constant scale factor (2x) exists between each layer, so if this information is provided for the top layer, the receiver can infer the locations of the attribute data for other layers. However, in the case of displacement data, such a constant relationship often does not exist, so the packing information of the displacement data must be provided for each layer.

[0287] Fig. 22 is a diagram showing another example of the syntax structure of scalable_packed_video_layer_info (payloadSize) according to embodiments. The present disclosure may refer to scalable_packed_video_layer_info (payloadSize) as scalable coding information. That is, Fig. 22 shows a method of transmitting displacement packing information in units of layers through a scalable Packed video layer information SEI message in the present disclosure. That is, Fig. 22 extends the scalable packed video coding layer information of Fig. 21 to further include information indicating the displacement information position within a packed video frame, a packing method of the displacement information, etc.

[0288] In Fig. 22, single_lod_displacement_flag is a flag that indicates how geometry (displacement) data is mapped to each layer of scalable coded packed video.

[0289] According to embodiments, the receiving device can infer up to which LoD level (i.e., level) displacement data belonging to each layer is included by using single_lod_displacement_flag. If the value of single_lod_displacement_flag is '1', it indicates that each layer includes displacement data corresponding to one LoD. If the value of single_lod_displacement_flag is '0', additional information is used to determine the number of LoDs of displacement data belonging to each layer.

[0290] displacement_Reverse_Packing_flag indicates that displacement data is packed in the reverse direction of the image (i.e., starting from the end of the image and packing in reverse order) when 1, and that it is packed in the forward direction of the image (i.e., starting from the beginning of the image and packing in forward order) when 0. This flag can also be placed in the standard asps (Atlas sequence parameter set).

[0291] num_lod_displacement[j] represents the number of LoDs of displacement data included in the jth layer and is defined as an integer with a minimum value of 1. Based on this information, the receiving device can select a layer to decode according to the target LoD for performing 3D mesh reconstruction.

[0292] displacement_region_top_left_x[j], displacement_region_top_left_y[j] represent the upper left coordinates of the region where displacement data is located within the packed video frame decoded up to the jth layer.

[0293] displacement_region_width_minus1[j] and displacement_region_height_minus1[j] represent the width and height of the region where displacement data is located within the packed video frame decoded up to the jth layer.

[0294] In addition to this embodiment, other methods for providing position information within a packed video frame of displacement data are possible, and this can be done by adding such information using a method such as extending packing_information, extending vps_packed_video_extension, or extending vps_vdmc_extension.

[0295] Fig. 23 is a block diagram illustrating another example of a receiving device according to embodiments. The receiving device of Fig. 23 may be referred to as a dynamic mesh content receiving device.

[0296] According to embodiments, a bitstream of mesh data encapsulated in a file from a transmitting device and delivered to a receiving device via a delivery module is decapsulated in a file decapsulation module. If the bitstream of mesh data is not encapsulated in a file format from the transmitting device, the decapsulation process is omitted at the receiving device.

[0297] According to embodiments, the mesh data decoding module separates the bitstream of mesh data into a base mesh bitstream and a scalable texture & displacement bitstream (or PVD bitstream), and then performs decoding on each.

[0298] The following is a detailed description of the process of performing scalable decoding based on signaling information in the receiving device of FIG. 23.

[0299] When scalable coding information is signaled as an extension of the V3C parameter set.

[0300] 1) The stored and / or received dynamic mesh content passes through the delivery module and the file decapsulation module and can be in a form similar to the bitstream structure of FIG. 15 (i.e., dynamic mesh bitstream).

[0301] 2) The bitstream parser inside the mesh data decoding module can play a role in parsing the dynamic mesh bitstream.

[0302] 3) The bitstream parser parses the V3C unit header and V3C unit payload that constitute the bitstream, and can obtain data corresponding to the unit type V3C_VPS defined in Fig. 16, i.e., VPS data.

[0303] 4) The receiving device can obtain codec information for signaled scalable coding by parsing the profile_tier_level() information included in the VPS data obtained in step 3) above (see FIGS. 19 and 20). Based on the obtained codec information for scalable coding, the receiving device can determine whether the receiver supports the corresponding codec, and predict and determine subsequent decoding operations.

[0304] 5) In addition, the receiving device can obtain the extension information, i.e., scalable coding information, signaled in the VPS data (e.g., vps_packed_video_extension, packing_information) obtained in the above process 3) (see the method of signaling scalability information for packed video described in FIGS. 19 and 20).

[0305] 6) The receiving device can obtain scalable coding information from the above process 5), that is, scalable packed video coding layer information defined in FIG. 22, and obtain information such as the scalable coding type included in the bitstream, the number of layers, and / or the mapping of layers and LoD, as described in the scalable coding syntax.

[0306] 7) The receiving device can predict and determine subsequent decoding operations by considering and / or judging available resources of the receiving device based on the scalable coding information obtained in the above process 6).

[0307] 8) In the method proposed in the present disclosure, the receiving device can identify the geometry and texture data information scalably coded in the bitstream of the dynamic mesh content prior to the direct decoding process of the packed video data through the processes 1) to 7).

[0308] 9) The receiving device can determine displacement information based on the number of displacement vertices calculated for each LoD through the decoded data according to the information of Fig. 22, if displacement_Reverse_Packing_flag (i.e., reversepacking_flag) is 1. If it is 0, the receiving device can determine displacement information of each layer according to the information of Fig. 22 to reconstruct dynamic mesh data.

[0309] Fig. 24 is a flowchart showing an example of a transmission method according to embodiments. The transmission method according to embodiments may include a step of encoding mesh data (S31011) and a step of transmitting a bitstream including the encoded mesh data (S31012). In one embodiment, the bitstream transmitted in step (S31012) includes a base mesh bitstream and a scalable texture & displacement bitstream (or PVD bitstream).

[0310] According to embodiments, the step of encoding mesh data (S31011) may include a process of encoding a base mesh, a process of packing and scalable encoding displacement vectors or displacement vector transformation coefficients and texture maps into one frame in units of layers, and a process of signaling related signaling information. Here, the layer units may be a base layer and one or more enhancement layers. The process of packing and scalable encoding displacement vectors or displacement vector transformation coefficients and texture maps into one frame in units of layers in the step of encoding mesh data (S31011) and the process of signaling related signaling information will be described with reference to the descriptions of FIGS. 15 to 17 and FIGS. 19 to 22, and are omitted here to avoid redundant description.

[0311] In the step (S31012) of transmitting a bitstream including the above mesh data, the base mesh bitstream and the scalable texture & displacement bitstream (or PVD bitstream) generated as described above in the step (S31011) of encoding the mesh data are generated as one bitstream as shown in FIG. 15, and transmitted to a receiving device through a transmitting unit.

[0312] Fig. 25 is a flowchart showing an example of a receiving method according to embodiments. The receiving method according to embodiments may include a step (S32011) of receiving a bitstream including mesh data and a step (S32012) of decoding the mesh data included in the bitstream. The step (S32011) of receiving a bitstream including mesh data demultiplexes a base mesh bitstream and a scalable texture & displacement bitstream (or PVD bitstream) from the received bitstream. In the step (S32012) of decoding the mesh data, scalable decoding is performed on the scalable texture & displacement bitstream (or PVD bitstream) based on signaling information as in Fig. 18 or Fig. 23, and a process of dividing a texture map and displacement information from a target frame and reconstructing dynamic mesh data is performed. In the step of decoding mesh data (S32012), the process of decoding packed video data and reconstructing dynamic mesh data refers to the description of FIG. 18 and / or FIG. 23 and is omitted here to avoid redundant description.

[0313] As explained so far, the method proposed in the present disclosure defines the syntax (i.e., signaling information) required when applying scalable coding according to a predefined criterion and / or a newly defined LoD value in order to pack and integrate geometry data (i.e., displacement information) and texture data (attribute information or texture map) among the data constituting dynamic mesh content into one frame.

[0314] According to embodiments, geometry data and texture data of dynamic mesh content can be encoded as layer-based scalable coded packed video data in a spatial or temporal manner, etc., according to scalable coding syntax (or scalable coding information).

[0315] According to embodiments, scalable coding-related information such as codec information, layer information, LoD, etc. related to scalable coded geometry data and texture data can be signaled at the parameter set level of the bitstream constituting the dynamic mesh content.

[0316] Accordingly, the dynamic mesh content receiving device can efficiently access the bitstream constituting the dynamic mesh content since it can determine whether there is data to which scalable coding has been applied within the content before actually decoding the geometry data and texture data encoded with the video codec.

[0317] Additionally, by packing geometry data and texture data into one frame at a time, synchronization issues between data can be minimized, enabling efficient scalable coding services to be provided.

[0318] In addition, the dynamic mesh content receiving device can effectively decode and render scalable coded data in whole or in a selective manner, depending on the hardware constraints of the receiving device, such as resources and display, and / or the intent and profile definition of the content creator, user, or receiver itself.

[0319] Each of the parts, modules, or units described above may be software, processors, or hardware parts that execute sequential execution processes stored in memory (or storage units). Each of the steps described in the embodiments described above may be performed by processors, software, or hardware parts. Each of the modules / blocks / units described in the embodiments described above may operate as a processor, software, or hardware. In addition, the methods presented in the embodiments may be implemented as code. This code may be written on a processor-readable storage medium and thus may be read by a processor provided by an apparatus.

[0320] Furthermore, throughout the specification, when a part is said to "include" a component, this does not exclude other components, unless otherwise specifically stated, but rather implies the inclusion of other components. Furthermore, terms such as "part" described in the specification mean a unit that processes at least one function or operation, which may be implemented using hardware, software, or a combination of hardware and software.

[0321] For convenience of explanation, this specification has been described separately in each drawing. However, it is also possible to design new embodiments by combining the embodiments described in each drawing. Furthermore, designing a computer-readable recording medium containing a program for executing the previously described embodiments, as required by those skilled in the art, is also within the scope of the embodiments.

[0322] The devices and methods according to the embodiments are not limited to the configurations and methods of the embodiments described above, but the embodiments may be configured by selectively combining all or part of each embodiment so that various modifications can be made.

[0323] Although preferred embodiments of the embodiments have been illustrated and described, the embodiments are not limited to the specific embodiments described above, and various modifications may be made by those skilled in the art to which the present disclosure pertains without departing from the spirit or scope of the embodiments claimed in the claims, and such modifications should not be understood individually from the technical idea or prospect of the embodiments.

[0324] The various components of the devices of the embodiments may be implemented by hardware, software, firmware, or a combination thereof. The various components of the embodiments may be implemented by a single chip, for example, a single hardware circuit. The components according to the embodiments may be implemented by separate chips. At least one of the components of the devices of the embodiments may be configured with one or more processors capable of executing one or more programs, and the one or more programs may perform, or include instructions for performing, one or more of the operations / methods according to the embodiments. The executable instructions for performing the methods / operations of the devices of the embodiments may be stored in non-transitory CRMs or other computer program products configured to be executed by one or more processors, or may be stored in temporary CRMs or other computer program products configured to be executed by one or more processors. In addition, the memory according to the embodiments may be used as a concept including not only volatile memory (e.g., RAM, etc.), but also non-volatile memory, flash memory, PROM, etc. Additionally, it may include implementations in the form of carrier waves, such as transmissions via the Internet. Furthermore, processor-readable recording media may be distributed across network-connected computer systems, allowing processor-readable code to be stored and executed in a distributed manner.

[0325] In this document, " / " and "," are interpreted as "and / or". For example, "A / B" is interpreted as "A and / or B", and "A, B" is interpreted as "A and / or B". Additionally, "A / B / C" means "at least one of A, B, and / or C". Also, "A, B, C" means "at least one of A, B, and / or C". Additionally, "or" in this document is interpreted as "and / or". For example, "A or B" can mean 1) "A" only, 2) "B" only, or 3) "A and B". In other words, "or" in this document can mean "additionally or alternatively".

[0326] Various elements of the embodiments may be implemented by hardware, software, firmware, or a combination thereof. Various elements of the embodiments may be implemented on a single chip, such as a hardware circuit. In some embodiments, the embodiments may optionally be implemented on separate chips. In some embodiments, at least one of the elements of the embodiments may be implemented within one or more processors that include instructions for performing operations according to the embodiments.

[0327] Additionally, the operations according to the embodiments described in this document may be performed by a transceiver device including one or more memories and / or one or more processors according to the embodiments. One or more memories may store programs for processing / controlling the operations according to the embodiments, and one or more processors may control various operations described in this document. One or more processors may be referred to as a controller, etc. The operations according to the embodiments may be performed by firmware, software, and / or a combination thereof, and the firmware, software, and / or a combination thereof may be stored in a processor or a memory.

[0328] Terms such as "first" and "second" may be used to describe various components of the embodiments. However, the various components according to the embodiments should not be interpreted in a limited manner by these terms. These terms are merely used to distinguish one component from another. For example, a first user input signal may be referred to as a "second user input signal." Similarly, a second user input signal may be referred to as a "first user input signal." The use of these terms should be interpreted as not departing from the scope of the various embodiments. Although "first user input signal" and "second user input signal" are both user input signals, they do not necessarily mean the same user input signals unless the context clearly indicates otherwise.

[0329] The terminology used to describe the embodiments is for the purpose of describing particular embodiments and is not intended to be limiting of the embodiments. As used in the description of the embodiments and in the claims, the singular is intended to include the plural unless the context clearly dictates otherwise. The expressions “and / or” are used to mean all possible combinations of the terms. The expression “comprises” or “includes” describes the presence of features, numbers, steps, elements, and / or components, but does not mean that additional features, numbers, steps, elements, and / or components are not included. Conditional expressions such as “if” or “when” used to describe the embodiments are not intended to be limited to only optional cases. When a specific condition is satisfied, a related action is performed in response to a specific condition, or a related definition is intended to be interpreted.

[0330] As described above, the relevant contents have been described in the best form for carrying out the embodiments.

[0331] As described above, the embodiments may be applied, in whole or in part, to mesh data transmission and reception devices and systems. Those skilled in the art will appreciate that various modifications and variations may be made to the embodiments within the scope of the embodiments. The embodiments may include modifications and variations, and such modifications and variations do not depart from the scope of the claims and their equivalents.

Claims

1. A step of receiving a bitstream containing mesh data; and A step of decoding the above mesh data; comprising: How to decode.

2. In the first paragraph, the step of decoding the mesh data A base mesh processing step for restoring a base mesh from a base mesh bitstream included in the above bitstream; A packed video data processing step for separating and restoring displacement information and attribute information from a packed video data bitstream included in the bitstream based on signaling information; and A decoding method comprising a restoration step of restoring a mesh based on the base mesh and the displacement information.

3. In the second paragraph, the packed video data processing step A step of scalably decoding packed video data from the packed video data bitstream based on a layer basis; and A decoding method comprising a step of separating and restoring displacement information and attribute information from packed video data of the decoded target packed video frame based on the signaling information.

4. In the third paragraph, the signaling information is A decoding method including information for identifying the location of the displacement information within the target packed video frame.

5. In paragraph 3, A decoding method in which the above signaling information is carried via a SEI (Supplemental enhancement information) message.

6. Memory; and comprising at least one processor connected to said memory, At least one processor of the above: Receiving a bitstream containing mesh data; and Decode the above mesh data; configured to do so, Decoding device.

7. In the 6th paragraph, at least one processor A base mesh processing unit for restoring a base mesh from a base mesh bitstream included in the above bitstream; A packed video data processing unit that separates and restores displacement information and attribute information from a packed video data bitstream included in the bitstream based on signaling information; and A decoding device including a mesh restoration unit that restores a mesh based on the base mesh and the displacement information.

8. In the 7th paragraph, the packed video data processing unit A decoding device that scalably decodes packed video data from the packed video data bitstream based on a layer basis, and separates and restores displacement information and attribute information from the packed video data of the decoded target packed video frame based on the signaling information.

9. In paragraph 8, the signaling information is A decoding device including information for identifying the location of the displacement information within the target packed video frame.

10. In paragraph 8, A decoding device in which the above signaling information is carried via a SEI (Supplemental enhancement information) message.

11. Step of encoding mesh data; and A step of transmitting a bitstream including the encoded mesh data; comprising: Encoding method.

12. In the 11th paragraph, the step of encoding the mesh data A step of generating a base mesh bitstream by encoding a base mesh generated by simplifying the original mesh; A step of generating displacement information based on the above base mesh; A step of generating attribute information based on the original mesh and the displacement information; A step of packing the displacement information and the attribute information into a packed video frame in layers and scalably encoding them to generate a packed video data bitstream; and An encoding method comprising a step of generating signaling information for restoration of the displacement information and the attribute information.

13. In paragraph 12, the signaling information is A decoding method including information for identifying the location of the displacement information within the target packed video frame.

14. In paragraph 12, A decoding method in which the above signaling information is carried via a SEI (Supplemental enhancement information) message.

15. A computer-readable storage medium storing a bitstream generated by the method according to Article 11.

16. Step of obtaining bitstream for image information; wherein the bitstream is generated based on a step of encoding mesh data and a step of transmitting a bitstream including the encoded mesh data; and A method comprising the step of transmitting data including the bitstream.

Images