Encoding method, decoding method, encoding device, and decoding device

Abstract

This encoding method comprises: acquiring a plurality of vertices included in a three-dimensional mesh (S1561); generating a plurality of two-dimensional coordinates by projecting the plurality of vertices onto a two-dimensional plane (S1562); transforming the plurality of two-dimensional coordinates using a two-dimensional transformation on the basis of parameters (S1563); and generating a bitstream including the parameters (S1564). The plurality of two-dimensional coordinates obtained through the two-dimensional transformation are used to map the texture of the three-dimensional mesh.

Description

Encoding method, decoding method, encoding device, and decoding device

[0001] The present disclosure relates to encoding methods and the like.

[0002] In US Pat. No. 6,269,549 a method and apparatus for encoding and decoding three-dimensional mesh data is proposed.

[0003] Japanese Patent Application Laid-Open No. 2006-187015

[0004] Further improvements are desired for the encoding or decoding process for three-dimensional meshes.The present disclosure aims to improve the encoding or decoding process for three-dimensional meshes.

[0005] An encoding method according to one aspect of the present disclosure includes obtaining a plurality of vertices contained in a three-dimensional mesh, projecting the plurality of vertices onto a two-dimensional plane to generate a plurality of two-dimensional coordinates, performing two-dimensional transformation on the plurality of two-dimensional coordinates based on parameters, generating a bitstream including the parameters, and using the plurality of two-dimensional coordinates after the two-dimensional transformation to map a texture of the three-dimensional mesh.

[0006] A decoding method according to one aspect of the present disclosure includes obtaining a bitstream, obtaining from the bitstream a plurality of vertices and parameters contained in a three-dimensional mesh, projecting the plurality of vertices onto a two-dimensional plane to generate a plurality of two-dimensional coordinates, performing a two-dimensional transformation on the plurality of two-dimensional coordinates based on the parameters, and using the plurality of two-dimensional coordinates after the two-dimensional transformation to map a texture onto the three-dimensional mesh.

[0007] These comprehensive or specific aspects may be realized as a system, an apparatus, an integrated circuit, a computer program, or a computer-readable recording medium such as a CD-ROM, or may be realized as any combination of a system, an apparatus, an integrated circuit, a computer program, and a recording medium.

[0008] The present disclosure may contribute to improvements in encoding processes and the like related to three-dimensional meshes.

[0009] 1 is a conceptual diagram showing a three-dimensional mesh according to an embodiment. FIG. 2 is a conceptual diagram showing basic elements of a three-dimensional mesh according to an embodiment. FIG. 3 is a conceptual diagram showing mapping according to an embodiment. FIG. 4 is a block diagram showing a configuration example of an encoding / decoding system according to an embodiment. FIG. 5 is a block diagram showing a configuration example of an encoding device according to an embodiment. FIG. 6 is a block diagram showing another configuration example of an encoding device according to an embodiment. FIG. 7 is a block diagram showing another configuration example of a decoding device according to an embodiment. FIG. 8 is a block diagram showing another configuration example of a decoding device according to an embodiment. FIG. 9 is a block diagram showing another configuration example of a decoding device according to an embodiment. FIG. 10 is a conceptual diagram showing another configuration example of a bit stream according to an embodiment. FIG. 11 is a conceptual diagram showing yet another configuration example of a bit stream according to an embodiment. FIG. 12 is a block diagram showing a specific example of an encoding / decoding system according to an embodiment. FIG. 13 is a conceptual diagram showing an example configuration of point cloud data according to an embodiment. FIG. 14 is a conceptual diagram showing an example data file of point cloud data according to an embodiment. FIG. 15 is a conceptual diagram showing an example configuration of mesh data according to an embodiment. FIG. 16 is a conceptual diagram showing an example data file of mesh data according to an embodiment. FIG. 17 is a conceptual diagram showing types of three-dimensional data according to an embodiment. FIG. 18 is a block diagram showing an example configuration of a three-dimensional data encoder according to an embodiment. FIG. 19 is a block diagram showing an example configuration of a three-dimensional data decoder according to an embodiment. FIG. 19 is a block diagram showing another configuration example of a three-dimensional data encoder according to an embodiment. FIG. 19 is a block diagram showing another configuration example of a three-dimensional data decoder according to an embodiment. 1 is a conceptual diagram showing a specific example of encoding processing according to an embodiment. FIG. 2 is a conceptual diagram showing a specific example of decoding processing according to an embodiment. FIG. 3 is a block diagram showing an implementation example of an encoding device according to an embodiment. FIG. 4 is a block diagram showing an implementation example of a decoding device according to an embodiment. FIG. 5 is a block diagram showing another configuration example of an encoding / decoding system according to an embodiment. FIG. 6 is a block diagram showing another configuration example of an encoding device according to an embodiment. FIG. 7 is a block diagram showing another configuration example of a decoding device according to an embodiment. FIG. 8 is a block diagram showing another configuration example of an encoding device according to an embodiment. FIG. 9 is a block diagram showing another configuration example of a decoding device according to an embodiment. FIG. 10 is a flow diagram showing processing of an encoding device according to an embodiment. FIG. 11 is an explanatory diagram conceptually showing encoding of a mesh frame according to an embodiment. FIG. 12 is a flow diagram showing processing of a decoding device according to an embodiment.1 is an explanatory diagram conceptually illustrating decoding of a mesh frame according to an embodiment. FIG. 2 is a block diagram illustrating an example configuration of a decoding device according to an embodiment. FIG. 3 is a block diagram illustrating an example configuration of a decoding device according to an embodiment. FIG. 4 is an explanatory diagram illustrating an example of subdivision according to an embodiment. FIG. 5 is an explanatory diagram illustrating an example of displacement of vertices after displacement after subdivision according to an embodiment. FIG. 6 is an explanatory diagram illustrating an example of vertices of an original mesh according to an embodiment. FIG. 7 is an explanatory diagram illustrating an example of a mesh according to an embodiment. FIG. 8 is an explanatory diagram illustrating an example of division of a mesh into submeshes according to an embodiment. FIG. 9 is a first explanatory diagram illustrating an example of packing of displacement information into an image frame according to an embodiment. FIG. 10 is a second explanatory diagram illustrating an example of packing of displacement information into an image frame according to an embodiment. FIG. 11 is a third explanatory diagram illustrating an example of packing of displacement information into an image frame according to an embodiment. FIG. 12 is a diagram illustrating an example configuration of an encoding device in the case of division into multiple submeshes according to an embodiment. FIG. 13 is a diagram illustrating an example configuration of a preprocessor according to an embodiment. FIG. 14 is a diagram illustrating an example configuration of a decoding device in the case of division into multiple submeshes according to an embodiment. FIG. 15 is a diagram for explaining post-decoding processing according to an embodiment. FIG. 16 is a flowchart illustrating an example of decoding processing of a 3D mesh according to an embodiment. FIG. 17 is a diagram illustrating an example of different two-dimensional surfaces according to an embodiment. FIG. 18 is a diagram illustrating an example of three-dimensional rotation of a set of vertex coordinates around the z-axis according to an embodiment. 15 is a diagram illustrating an example of three-dimensionally rotating a set of vertex coordinates around the z-axis according to an embodiment. FIG. 16 is a diagram illustrating an example of projecting vertex coordinates onto a two-dimensional surface according to an embodiment. FIG. 17 is a diagram illustrating an example of Apple scaling a set of two-dimensional coordinates according to an embodiment. FIG. 18 is a flowchart illustrating an example of the scaling process in step S1505 and the normalization process in S1506 according to an embodiment. FIG. 19 is a flowchart illustrating another example of the scaling process in step S1505 and the normalization process in S1506 according to an embodiment. FIG. 20 is a flowchart illustrating a modified example of step S1505 according to an embodiment. FIG. 21 is a diagram illustrating an example of two-dimensional rotation according to an embodiment. FIG. 22 is a flowchart illustrating another modified example of step S1505 according to an embodiment. FIG. 23 is a diagram illustrating an example of shifting (translating) a set of two-dimensional coordinates according to an embodiment.FIG. 1 is a diagram showing an example of syntax in the present disclosure according to an embodiment. FIG. 2 is a diagram showing another example of syntax in the present disclosure according to an embodiment. FIG. 3 is a flowchart showing an example of a coding process for a 3D mesh according to an embodiment. FIG. 4 is a diagram showing an example of the configuration of a coding device according to an embodiment. FIG. 5 is a flowchart showing an example of a coding method by a coding device according to an embodiment. FIG. 6 is a diagram showing an example of the configuration of a decoding device according to an embodiment. FIG. 7 is a flowchart showing an example of a decoding method by a decoding device according to an embodiment.

[0010] <Summary of the Disclosure> Three-dimensional (3D) meshes are used in computer graphics images, for example, which may be composed of multiple temporally distinct frames, each of which may be represented by a 3D mesh.

[0011] A 3D mesh is composed of vertex information indicating the positions of each of the vertices in 3D space, connectivity information indicating the connections between the vertices, and attribute information indicating the attributes of each vertex or face. Each face is constructed according to the connectivity between the vertices. Various computer graphics images can be expressed using such 3D meshes.

[0012] Furthermore, for transmission and storage of the 3D mesh, efficient encoding and decoding of the 3D mesh is expected. For efficient encoding and decoding of the 3D mesh, arithmetic coding and decoding may be used.

[0013] Further improvements are desired in the encoding or decoding process for three-dimensional data. The present disclosure aims to improve the encoding or decoding process for three-dimensional data.

[0014] Below, examples of inventions that can be obtained from the disclosure of this specification will be given, and the effects and the like that can be obtained from these inventions will be explained.

[0015] An encoding method according to a first aspect of the present disclosure obtains a plurality of vertices contained in a three-dimensional mesh, projects the plurality of vertices onto a two-dimensional plane to generate a plurality of two-dimensional coordinates, performs two-dimensional transformation on the plurality of two-dimensional coordinates based on parameters, generates a bitstream including the parameters, and uses the plurality of two-dimensional coordinates after the two-dimensional transformation to map a texture of the three-dimensional mesh.

[0016] This generates a bitstream containing parameters as information for identifying the area to which the texture of a three-dimensional mesh is to be mapped, so that a decoding device that acquires the bitstream can identify the area of ​​the texture to be mapped to the three-dimensional mesh based on multiple vertices and parameters.

[0017] An encoding method according to a second aspect of the present disclosure is the encoding method according to the first aspect, wherein the two-dimensional transformation includes a process of scaling the plurality of two-dimensional coordinates, and the parameters include a scaling rate.

[0018] This allows the decoding device to know the scaling ratios of multiple two-dimensional coordinates, so that the decoding device can identify the area of ​​the texture to be mapped onto the three-dimensional mesh.

[0019] An encoding method according to a third aspect of the present disclosure is an encoding method according to the first aspect, wherein the two-dimensional transformation includes a process of shifting the positions of the multiple two-dimensional coordinates, and the parameters include an offset amount for the shift.

[0020] This allows the decoding device to be informed of the offset amounts in shifting multiple two-dimensional coordinates, allowing the decoding device to identify the area of ​​the texture to be mapped onto the three-dimensional mesh.

[0021] An encoding method according to a fourth aspect of the present disclosure is the encoding method according to the first aspect, wherein the two-dimensional transformation includes a process of two-dimensionally rotating the plurality of two-dimensional coordinates, and the parameters include a rotation angle of the two-dimensional rotation.

[0022] This allows the decoding device to be informed of the rotation angles of the two-dimensional rotation of multiple two-dimensional coordinates, allowing the decoding device to identify the area of ​​the texture to be mapped onto the three-dimensional mesh.

[0023] An encoding method according to a fifth aspect of the present disclosure is an encoding method according to any one of the first to fourth aspects, wherein the projection involves rotating the three-dimensional mesh three-dimensionally in three-dimensional space and projecting the three-dimensional mesh after the three-dimensional rotation onto the two-dimensional plane, and the bitstream includes a rotation angle of the three-dimensional rotation.

[0024] This allows the decoding device to know the rotation angle of the three-dimensional rotation of the three-dimensional mesh, so that the decoding device can identify the area of ​​the texture to be mapped onto the three-dimensional mesh.

[0025] An encoding method according to a sixth aspect of the present disclosure is the encoding method according to the second aspect, wherein the scaling ratio includes at least one of an upscale parameter used in the enlargement process and a downscale parameter used in the reduction process.

[0026] An encoding method according to a seventh aspect of the present disclosure is the encoding method according to the sixth aspect, wherein the scaling ratio is expressed as a fraction with the upscale parameter as the numerator and the downscale parameter as the denominator.

[0027] An encoding method according to an eighth aspect of the present disclosure is the encoding method according to the sixth or seventh aspect, wherein at least one of the upscale parameter and the downscale parameter is an integer.

[0028] An encoding method according to a ninth aspect of the present disclosure is the encoding method according to the sixth or seventh aspect, wherein at least one of the upscale parameter and the downscale parameter is a power of two.

[0029] A decoding method according to a tenth aspect of the present disclosure includes obtaining a bitstream, obtaining from the bitstream a plurality of vertices and parameters contained in a three-dimensional mesh, projecting the plurality of vertices onto a two-dimensional plane to generate a plurality of two-dimensional coordinates, performing a two-dimensional transformation on the plurality of two-dimensional coordinates based on the parameters, and using the plurality of two-dimensional coordinates after the two-dimensional transformation to map a texture onto the three-dimensional mesh.

[0030] According to this, since the information is obtained from a bitstream that includes parameters as information for identifying the area of ​​the texture to be mapped to the three-dimensional mesh, the decoding device that has obtained the bitstream can identify the area of ​​the texture to be mapped to the three-dimensional mesh based on multiple vertices and parameters.

[0031] A decoding method according to an eleventh aspect of the present disclosure is the decoding method according to the tenth aspect, wherein the two-dimensional transformation includes a process of scaling the plurality of two-dimensional coordinates, and the parameters include a scaling rate.

[0032] This allows the scaling ratios of multiple two-dimensional coordinates to be obtained, making it possible to identify the area of ​​the texture to be mapped onto the three-dimensional mesh.

[0033] A decoding method according to a twelfth aspect of the present disclosure is a decoding method according to the tenth aspect, wherein the two-dimensional transformation includes a process of shifting the positions of the multiple two-dimensional coordinates, and the parameters include an offset amount for the shift.

[0034] This makes it possible to obtain the offset amounts for shifting a plurality of two-dimensional coordinates, thereby making it possible to identify the area of ​​the texture to be mapped onto the three-dimensional mesh.

[0035] A decoding method according to a thirteenth aspect of the present disclosure is a decoding method according to the tenth aspect, wherein the two-dimensional transformation includes a process of two-dimensionally rotating the plurality of two-dimensional coordinates, and the parameters include a rotation angle of the two-dimensional rotation.

[0036] This makes it possible to obtain the rotation angles of the two-dimensional rotation of a plurality of two-dimensional coordinates, thereby making it possible to identify the area of ​​the texture to be mapped onto the three-dimensional mesh.

[0037] A decoding method according to a fourteenth aspect of the present disclosure is a decoding method according to any one of the tenth to thirteenth aspects, wherein the projection involves rotating the three-dimensional mesh three-dimensionally in three-dimensional space, and projecting the three-dimensional mesh after the three-dimensional rotation onto the two-dimensional plane, and the bit stream includes a rotation angle of the three-dimensional rotation.

[0038] This makes it possible to obtain the rotation angle of the three-dimensional rotation of the three-dimensional mesh, thereby making it possible to identify the area of ​​the texture to be mapped onto the three-dimensional mesh.

[0039] A decoding method according to a fifteenth aspect of the present disclosure is an encoding method according to the eleventh aspect, wherein the scaling ratio includes at least one of an upscale parameter used in the enlargement process and a downscale parameter used in the reduction process.

[0040] A decoding method according to a sixteenth aspect of the present disclosure is the encoding method according to the fifteenth aspect, wherein the scaling ratio is expressed as a fraction with the upscale parameter as the numerator and the downscale parameter as the denominator.

[0041] A decoding method according to a seventeenth aspect of the present disclosure is the decoding method according to the fifteenth or sixteenth aspect, wherein at least one of the upscale parameter and the downscale parameter is an integer.

[0042] A decoding method according to an eighteenth aspect of the present disclosure is the decoding method according to the fifteenth or sixteenth aspect, wherein at least one of the upscale parameter and the downscale parameter is a power of two.

[0043] A coding device according to a nineteenth aspect of the present disclosure includes a circuit and a memory connected to the circuit, wherein the circuit, in operation, acquires a plurality of vertices included in a three-dimensional mesh, projects the plurality of vertices onto a two-dimensional plane to generate a plurality of two-dimensional coordinates, performs two-dimensional transformation on the plurality of two-dimensional coordinates based on parameters, generates a bitstream including the parameters, and the plurality of two-dimensional coordinates after the two-dimensional transformation are used to map a texture of the three-dimensional mesh.

[0044] This generates a bitstream containing parameters as information for identifying the area to which the texture of a three-dimensional mesh is to be mapped, so that a decoding device that acquires the bitstream can identify the area of ​​the texture to be mapped to the three-dimensional mesh based on multiple vertices and parameters.

[0045] A decoding device according to a twentieth aspect of the present disclosure comprises a circuit and a memory connected to the circuit, wherein the circuit, in operation, acquires a bitstream, acquires from the bitstream a plurality of vertices and parameters contained in a three-dimensional mesh, projects the plurality of vertices onto a two-dimensional plane to generate a plurality of two-dimensional coordinates, performs a two-dimensional transformation on the plurality of two-dimensional coordinates based on the parameters, and uses the plurality of two-dimensional coordinates after the two-dimensional transformation to map a texture onto the three-dimensional mesh.

[0046] According to this, since the information is obtained from a bitstream that includes parameters as information for identifying the area of ​​the texture to be mapped to the three-dimensional mesh, the decoding device that has obtained the bitstream can identify the area of ​​the texture to be mapped to the three-dimensional mesh based on multiple vertices and parameters.

[0047] These comprehensive or specific aspects may be realized as a system, an apparatus, an integrated circuit, a computer program, or a recording medium such as a computer-readable CD-ROM, or may be realized as any combination of a system, an apparatus, an integrated circuit, a computer program, or a recording medium.

[0048] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0049] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection configurations, steps, and step order shown in the following embodiments are merely examples and are not intended to limit the present invention. Furthermore, among the components in the following embodiments, components that are not described in the independent claims that represent the highest concepts are described as optional components.

[0050] (Embodiment) In this embodiment, an encoding method, a decoding method, etc. will be described.

[0051] <Expressions and Terms> The following expressions and terms are used herein.

[0052] (1) Three-dimensional Mesh A three-dimensional mesh is a collection of multiple faces, and represents, for example, a three-dimensional object. A three-dimensional mesh is mainly composed of vertex information, connectivity information, and attribute information. A three-dimensional mesh may be expressed as a polygon mesh or a mesh. A three-dimensional mesh may also vary over time. A three-dimensional mesh may include metadata related to the vertex information, connectivity information, and attribute information, and may also include other additional information.

[0053] (2) Vertex Information Vertex information is information indicating a vertex. For example, the vertex information indicates the position of a vertex in a three-dimensional space. Furthermore, a vertex corresponds to a vertex of a face that constitutes a three-dimensional mesh. Vertex information may be expressed as "geometry." Furthermore, vertex information may be expressed as position information.

[0054] (3) Connection Information Connection information is information that indicates connections between vertices. For example, connection information indicates connections for forming faces or edges of a three-dimensional mesh. Connection information may be expressed as "Connectivity." Connection information may also be expressed as face information.

[0055] (4) Attribute Information Attribute information is information that indicates attributes of a vertex or a face. For example, attribute information indicates attributes such as a color, an image, and a normal vector associated with a vertex or a face. Attribute information may be expressed as "texture."

[0056] (5) Faces A face is an element that makes up a three-dimensional mesh. Specifically, a face is a polygon on a plane in three-dimensional space. For example, a face can be defined as a triangle in three-dimensional space.

[0057] (6) Plane A plane is a two-dimensional plane in a three-dimensional space. For example, a polygon is formed on a plane, and multiple polygons are formed on multiple planes.

[0058] (7) Bitstream: A bitstream corresponds to coded information. A bitstream may also be referred to as a stream, a coded bitstream, a compressed bitstream, or a coded signal.

[0059] (8) Encoding and Decoding The term encoding may be substituted with terms such as storing, including, writing, describing, signaling, sending, notifying, saving, or compressing, and these terms may be interchangeable. For example, encoding information may mean including the information in a bitstream. Also, encoding information into a bitstream may mean encoding the information to generate a bitstream that includes the encoded information.

[0060] Additionally, the term "decode" may be replaced with terms such as "read," "decode," "read," "load," "derive," "obtain," "receive," "extract," "reconstruct," "reconstruct," "decompress," or "decompress," and these terms may be interchangeable. For example, decoding information may mean obtaining information from a bitstream. Decoding information from a bitstream may mean decoding the bitstream to obtain information contained in the bitstream.

[0061] (9) Ordinal Numbers In the description, ordinal numbers such as first and second may be assigned to components, etc. These ordinal numbers may be changed as appropriate. Furthermore, new ordinal numbers may be assigned to components, etc., or removed. Furthermore, these ordinal numbers may be assigned to elements in order to identify them, and may not correspond to a meaningful order.

[0062] <Three-dimensional mesh> Fig. 1 is a conceptual diagram showing a three-dimensional mesh according to this embodiment. A three-dimensional mesh is composed of multiple faces. For example, each face is a triangle. The vertices of these triangles are defined in three-dimensional space. The three-dimensional mesh then represents a three-dimensional object. Each face may have a color or an image.

[0063] FIG. 2 is a conceptual diagram showing the basic elements of a three-dimensional mesh according to this embodiment. A three-dimensional mesh is composed of vertex information, connection information, and attribute information. The vertex information indicates the positions of the vertices of a face in three-dimensional space. The connection information indicates the connections between the vertices. A face can be identified by the vertex information and connection information. In other words, a colorless three-dimensional object is formed in three-dimensional space by the vertex information and connection information.

[0064] The attribute information may be associated with a vertex or a face. The attribute information associated with a vertex may be expressed as "Attribute Per Point." The attribute information associated with a vertex may indicate an attribute of the vertex itself, or may indicate an attribute of a face connected to the vertex.

[0065] For example, a color may be associated with a vertex as attribute information. The color associated with a vertex may be the color of the vertex itself, or the color of a face connected to the vertex. The color of a face may be the average of multiple colors associated with multiple vertices of the face. Furthermore, a normal vector may be associated with a vertex or a face as attribute information. Such a normal vector can represent the front and back of a face.

[0066] A two-dimensional image may be associated with a surface as attribute information. The two-dimensional image associated with a surface is also expressed as a texture image or an "Attribute Map." Information indicating mapping between the surface and the two-dimensional image may be associated with the surface as attribute information. Information indicating such mapping may be expressed as mapping information, vertex information of a texture image, texture coordinates, or "Attribute UV Coordinate."

[0067] Furthermore, information such as color, image, and moving image used as attribute information may be expressed as "parametric space."

[0068] The attribute information allows texture to be reflected on the three-dimensional object. That is, a three-dimensional object having color is formed in three-dimensional space based on the vertex information, connection information, and attribute information.

[0069] In the above, the attribute information is associated with the vertices or faces, but it may also be associated with the edges.

[0070] 3 is a conceptual diagram illustrating mapping according to this embodiment. For example, a region of a two-dimensional image on a two-dimensional plane can be mapped onto a surface of a three-dimensional mesh in three-dimensional space. Specifically, coordinate information of the region in the two-dimensional image is associated with the surface of the three-dimensional mesh. As a result, an image of the mapped region in the two-dimensional image is reflected on the surface of the three-dimensional mesh.

[0071] By using the mapping, the 2D image used as attribute information can be separated from the 3D mesh. For example, in encoding the 3D mesh, the 2D image may be encoded by an image encoding method or a video encoding method.

[0072] <System Configuration> Fig. 4 is a block diagram showing an example of the configuration of a coding / decoding system according to this embodiment. In Fig. 4, the coding / decoding system includes a coding device 100 and a decoding device 200.

[0073] For example, the encoding device 100 obtains a three-dimensional mesh and encodes the three-dimensional mesh into a bitstream. Then, the encoding device 100 outputs the bitstream to the network 300. For example, the bitstream includes the encoded three-dimensional mesh and control information for decoding the encoded three-dimensional mesh. By encoding the three-dimensional mesh, information about the three-dimensional mesh is compressed.

[0074] The network 300 transmits a bitstream from the encoding device 100 to the decoding device 200. The network 300 may be the Internet, a wide area network (WAN), a local area network (LAN), or a combination of these. The network 300 is not necessarily limited to bidirectional communication, and may be a unidirectional communication network for terrestrial digital broadcasting, satellite broadcasting, or the like.

[0075] Furthermore, the network 300 can be replaced by a recording medium such as a DVD (Digital Versatile Disc) or a BD (Blu-Ray Disc (registered trademark)).

[0076] The decoding device 200 obtains a bitstream and decodes a three-dimensional mesh from the bitstream. By decoding the three-dimensional mesh, information about the three-dimensional mesh is expanded. For example, the decoding device 200 decodes the three-dimensional mesh according to a decoding method corresponding to the encoding method used by the encoding device 100 to encode the three-dimensional mesh. That is, the encoding device 100 and the decoding device 200 perform encoding and decoding according to encoding methods and decoding methods that correspond to each other.

[0077] The 3D mesh before encoding may also be referred to as an original 3D mesh, and the 3D mesh after decoding may also be referred to as a reconstructed 3D mesh.

[0078] 5 is a block diagram showing an example of the configuration of a coding device 100 according to this embodiment. For example, the coding device 100 includes a vertex information encoder 101, a connection information encoder 102, and an attribute information encoder 103.

[0079] The vertex information encoder 101 is an electrical circuit that encodes vertex information. For example, the vertex information encoder 101 encodes the vertex information into a bitstream according to a format defined for the vertex information.

[0080] The connection information encoder 102 is an electrical circuit that encodes the connection information, for example, the connection information encoder 102 encodes the connection information into a bitstream according to a format defined for the connection information.

[0081] The attribute information encoder 103 is an electric circuit that encodes the attribute information. For example, the attribute information encoder 103 encodes the attribute information into a bit stream in accordance with a format defined for the attribute information.

[0082] The vertex information, connectivity information, and attribute information may be coded using variable-length coding or fixed-length coding, such as Huffman coding or context-adaptive binary arithmetic coding (CABAC).

[0083] The vertex information encoder 101, the connection information encoder 102, and the attribute information encoder 103 may be integrated together, or each of the vertex information encoder 101, the connection information encoder 102, and the attribute information encoder 103 may be further subdivided into multiple components.

[0084] 6 is a block diagram showing another example of the configuration of the encoding device 100 according to this embodiment. For example, the encoding device 100 includes a pre-processor 104 and a post-processor 105 in addition to the configuration shown in FIG.

[0085] The preprocessor 104 is an electrical circuit that performs processing before encoding the vertex information, connectivity information, and attribute information. For example, the preprocessor 104 may perform a conversion process, a separation process, a multiplexing process, or the like on the 3D mesh before encoding. More specifically, for example, the preprocessor 104 may separate the vertex information, connectivity information, and attribute information from the 3D mesh before encoding.

[0086] The post-processor 105 is an electrical circuit that performs processing after the vertex information, connection information, and attribute information are encoded. For example, the post-processor 105 may perform conversion processing, separation processing, multiplexing processing, or the like on the encoded vertex information, connection information, and attribute information. More specifically, for example, the post-processor 105 may multiplex the encoded vertex information, connection information, and attribute information into a bitstream. Furthermore, for example, the post-processor 105 may further perform variable-length coding on the encoded vertex information, connection information, and attribute information.

[0087] 7 is a block diagram showing an example of the configuration of a decoding device 200 according to this embodiment. For example, the decoding device 200 includes a vertex information decoder 201, a connection information decoder 202, and an attribute information decoder 203.

[0088] The vertex information decoder 201 is an electrical circuit that decodes vertex information. For example, the vertex information decoder 201 decodes vertex information from a bitstream according to a format defined for the vertex information.

[0089] The connection information decoder 202 is an electrical circuit that decodes the connection information, for example, the connection information decoder 202 decodes the connection information from the bitstream according to a format defined for the connection information.

[0090] The attribute information decoder 203 is an electric circuit that decodes the attribute information. For example, the attribute information decoder 203 decodes the attribute information from the bitstream in accordance with a format defined for the attribute information.

[0091] The vertex information, connection information, and attribute information may be decoded using variable length decoding or fixed length decoding, which may correspond to Huffman coding, context-adaptive binary arithmetic coding (CABAC), or the like.

[0092] The vertex information decoder 201, the connection information decoder 202, and the attribute information decoder 203 may be integrated together, or each of the vertex information decoder 201, the connection information decoder 202, and the attribute information decoder 203 may be further subdivided into multiple components.

[0093] 8 is a block diagram showing another example of the configuration of the decoding device 200 according to this embodiment. For example, the decoding device 200 includes a pre-processor 204 and a post-processor 205 in addition to the configuration shown in FIG.

[0094] The preprocessor 204 is an electrical circuit that performs processing before decoding the vertex information, connection information, and attribute information. For example, the preprocessor 204 may perform conversion processing, separation processing, multiplexing processing, or the like on the bitstream before decoding the vertex information, connection information, and attribute information.

[0095] More specifically, for example, the preprocessor 204 may separate a sub-bitstream corresponding to vertex information, a sub-bitstream corresponding to connectivity information, and a sub-bitstream corresponding to attribute information from the bitstream. Also, for example, the preprocessor 204 may perform variable-length decoding on the bitstream in advance before decoding the vertex information, connectivity information, and attribute information.

[0096] The post-processor 205 is an electrical circuit that performs processing after the vertex information, connection information, and attribute information are decoded. For example, the post-processor 205 may perform conversion processing, separation processing, multiplexing processing, or the like on the decoded vertex information, connection information, and attribute information. More specifically, for example, the post-processor 205 may multiplex the decoded vertex information, connection information, and attribute information onto a three-dimensional mesh.

[0097] <Bitstream> Vertex information, connection information, and attribute information are coded and stored in a bitstream. The relationship between this information and the bitstream is shown below.

[0098] 9 is a conceptual diagram showing an example of the configuration of a bitstream according to this embodiment. In this example, connection information, vertex information, and attribute information are integrated in the bitstream. For example, the connection information, vertex information, and attribute information may be included in a single file.

[0099] Furthermore, multiple portions of this information may be stored sequentially, such as a first portion of connection information, a first portion of vertex information, a first portion of attribute information, a second portion of connection information, a second portion of vertex information, a second portion of attribute information, etc. These multiple portions may correspond to multiple portions that are different in time, multiple portions that are different in space, or multiple different faces.

[0100] Furthermore, the storage order of the connection information, vertex information, and attribute information is not limited to the above example, and a storage order different from the above example may be used.

[0101] 10 is a conceptual diagram showing another example of the configuration of a bitstream according to this embodiment. In this example, a plurality of files are included in the bitstream, and connection information, vertex information, and attribute information are stored in different files. Here, a file containing connection information, a file containing vertex information, and a file containing attribute information are shown, but the storage format is not limited to this example. For example, two types of information among the connection information, vertex information, and attribute information may be included in one file, and the remaining type of information may be included in another file.

[0102] Alternatively, the information may be split and stored in more files. For example, multiple pieces of connectivity information may be stored in multiple files, multiple pieces of vertex information may be stored in multiple files, or multiple pieces of attribute information may be stored in multiple files. These multiple pieces may correspond to multiple temporally different pieces, multiple spatially different pieces, or multiple different faces.

[0103] Furthermore, the storage order of the connection information, vertex information, and attribute information is not limited to the above example, and a storage order different from the above example may be used.

[0104] 11 is a conceptual diagram showing another example of the configuration of a bitstream according to this embodiment. In this example, the bitstream is composed of multiple separable sub-bitstreams, and connection information, vertex information, and attribute information are stored in different sub-bitstreams.

[0105] Here, a sub-bitstream containing connection information, a sub-bitstream containing vertex information, and a sub-bitstream containing attribute information are shown, but the storage format is not limited to this example.

[0106] For example, two types of information among the connection information, vertex information, and attribute information may be included in one sub-bitstream, and the remaining type of information may be included in another sub-bitstream. Specifically, attribute information of a two-dimensional image or the like may be stored in a sub-bitstream that complies with an image coding method, separate from the sub-bitstreams of the connection information and vertex information.

[0107] Also, each sub-bitstream may include multiple files, and multiple pieces of connectivity information may be stored in multiple files, multiple pieces of vertex information may be stored in multiple files, or multiple pieces of attribute information may be stored in multiple files.

[0108] 9, 10, and 11, and a storage order different from the above examples may be used. For example, the vertex information, connection information, and attribute information may be stored in the bitstream in this order. Alternatively, the connection information, connection information, and attribute information may be stored in the bitstream in any of the following orders: connection information, attribute information, and vertex information; vertex information, attribute information, and connection information; attribute information, connection information, and vertex information; or attribute information, vertex information, and connection information.

[0109] Furthermore, each of the connection information, vertex information, and attribute information may be divided into a plurality of data, and the plurality of data may be stored in a cyclical or random order within the bitstream.

[0110] 12 is a block diagram showing a specific example of an encoding / decoding system according to this embodiment. In FIG. 12, the encoding / decoding system includes a three-dimensional data encoding system 110, a three-dimensional data decoding system 210, and an external connector 310.

[0111] The three-dimensional data encoding system 110 includes a controller 111, an input / output processor 112, a three-dimensional data encoder 113, a three-dimensional data generator 115, and a system multiplexer 114. The three-dimensional data decoding system 210 includes a controller 211, an input / output processor 212, a three-dimensional data decoder 213, a system demultiplexer 214, a presenter 215, and a user interface 216.

[0112] In the three-dimensional data encoding system 110, sensor data is input from a sensor terminal to a three-dimensional data generator 115. The three-dimensional data generator 115 generates three-dimensional data, such as point cloud data or mesh data, from the sensor data and inputs it to a three-dimensional data encoder 113.

[0113] For example, the three-dimensional data generator 115 generates vertex information, and generates connection information and attribute information corresponding to the vertex information. The three-dimensional data generator 115 may process the vertex information when generating the connection information and attribute information. For example, the three-dimensional data generator 115 may reduce the amount of data by deleting duplicate vertices, or may transform the vertex information (such as by shifting its position, rotating it, or normalizing it). The three-dimensional data generator 115 may also render the attribute information.

[0114] Furthermore, although the three-dimensional data generator 115 is a component of the three-dimensional data encoding system 110 in FIG. 12, it may be arranged externally and independently of the three-dimensional data encoding system 110.

[0115] The sensor terminal that provides the sensor data for generating the three-dimensional data may be, for example, a moving body such as an automobile, a flying object such as an airplane, a mobile terminal, a camera, etc. Furthermore, a distance sensor such as a LIDAR, a millimeter wave radar, an infrared sensor, or a range finder, a stereo camera, or a combination of multiple monocular cameras may also be used as the sensor terminal.

[0116] The sensor data may be the distance (position) of the object, monocular camera images, stereo camera images, color, reflectance, sensor attitude, orientation, gyro, sensing position (GPS information or altitude), speed, acceleration, sensing time, temperature, air pressure, humidity, or magnetism.

[0117] The three-dimensional data encoder 113 corresponds to the encoding device 100 shown in FIG. 5 and other figures. For example, the three-dimensional data encoder 113 encodes three-dimensional data to generate encoded data. The three-dimensional data encoder 113 also generates control information when encoding the three-dimensional data. The three-dimensional data encoder 113 then inputs the encoded data together with the control information to the system multiplexer 114.

[0118] The encoding method for the three-dimensional data may be an encoding method using geometry or an encoding method using a video codec. Here, the encoding method using geometry may also be referred to as a geometry-based encoding method. The encoding method using a video codec may also be referred to as a video-based encoding method.

[0119] The system multiplexer 114 multiplexes the encoded data and control information input from the 3D data encoder 113 to generate multiplexed data using a specified multiplexing method. The system multiplexer 114 may multiplex other media such as video, audio, subtitles, application data, or document files, or reference time information, along with the encoded data and control information of the 3D data. Furthermore, the system multiplexer 114 may multiplex attribute information related to the sensor data or the 3D data.

[0120] For example, the multiplexed data may have a file format for storage or a packet format for transmission. As these formats, ISOBMFF or a format based on ISOBMFF may be used. Also, MPEG-DASH, MMT, MPEG-2 TS Systems, RTP, or the like may be used.

[0121] The multiplexed data is then output as a transmission signal to the external connector 310 by the input / output processor 112. The multiplexed data may be transmitted as a transmission signal by wire or wirelessly. Alternatively, the multiplexed data is stored in an internal memory or a storage device. The multiplexed data may be transmitted to a cloud server via the Internet or may be stored in an external storage device.

[0122] For example, the transmission or storage of the multiplexed data is performed by a method according to the medium for transmission or storage, such as broadcasting or communication. The communication protocol may be http, ftp, TCP, UDP, IP, or a combination thereof. Furthermore, a pull-type communication method or a push-type communication method may be used.

[0123] For wired transmission, Ethernet (registered trademark), USB, RS-232C, HDMI (registered trademark), coaxial cable, etc. may be used. For wireless transmission, 3GPP (registered trademark), 3G / 4G / 5G defined by IEEE, wireless LAN, Wi-Fi, Bluetooth, or millimeter wave may be used. For broadcasting, for example, DVB-T2, DVB-S2, DVB-C2, ATSC3.0, or ISDB-S3 may be used.

[0124] The sensor data may be input to the three-dimensional data generator 115 or the system multiplexer 114. The three-dimensional data or encoded data may be output as a transmission signal directly to the external connector 310 via the input / output processor 112. The transmission signal output from the three-dimensional data encoding system 110 is input to the three-dimensional data decoding system 210 via the external connector 310.

[0125] Furthermore, each operation of the three-dimensional data encoding system 110 may be controlled by a controller 111 that executes an application program.

[0126] In the three-dimensional data decoding system 210, a transmission signal is input to an input / output processor 212. The input / output processor 212 decodes multiplexed data having a file format or a packet format from the transmission signal and inputs the multiplexed data to a system demultiplexer 214. The system demultiplexer 214 obtains coded data and control information from the multiplexed data and inputs them to a three-dimensional data decoder 213. The system demultiplexer 214 may extract other media or reference time information from the multiplexed data.

[0127] The three-dimensional data decoder 213 corresponds to the decoding device 200 shown in Fig. 7 etc. For example, the three-dimensional data decoder 213 decodes three-dimensional data from the encoded data based on a predefined encoding method. The three-dimensional data is then presented to the user by the presenter 215.

[0128] Additionally, additional information such as sensor data may be input to the presenter 215. The presenter 215 may present three-dimensional data based on the additional information. Additionally, a user instruction may be input from a user terminal to the user interface 216. Then, the presenter 215 may present three-dimensional data based on the input instruction.

[0129] The input / output processor 212 may acquire the three-dimensional data and the encoded data from the external connector 310 .

[0130] Furthermore, each operation of the three-dimensional data decoding system 210 may be controlled by a controller 211 that executes an application program.

[0131] 13 is a conceptual diagram showing an example of the configuration of point cloud data according to this embodiment. The point cloud data is data of a group of points representing a three-dimensional object.

[0132] Specifically, a point cloud is made up of a plurality of points, and has position information indicating the three-dimensional coordinate position of each point and attribute information indicating the attribute of each point. The position information is also expressed as geometry.

[0133] The type of attribute information may be, for example, color, reflectance, etc. One point may be associated with attribute information of one type, one point may be associated with attribute information of multiple different types, or one point may be associated with attribute information having multiple values ​​for the same type.

[0134] 14 is a conceptual diagram showing an example of a data file of point cloud data according to this embodiment. This example shows a case where there is a one-to-one correspondence between position information items and attribute information items, and shows position information and attribute information for N points that make up the point cloud data. In this example, the position information is information indicating a three-dimensional coordinate position using three axes, x, y, and z, and the attribute information is information indicating a color using RGB. A PLY file or the like can be used as a representative data file for point cloud data.

[0135] 15 is a conceptual diagram showing an example of the configuration of mesh data according to this embodiment. Mesh data is data used in CG (Computer Graphics) and the like, and is three-dimensional mesh data that shows the three-dimensional shape of an object using multiple surfaces. Each surface is also expressed as a polygon, and has a polygonal shape such as a triangle or a rectangle.

[0136] Specifically, a 3D mesh is composed of a plurality of points constituting a point cloud, as well as a plurality of edges and a plurality of faces. Each point is also expressed as a vertex or a position. Each edge corresponds to a line segment connected by two vertices. Each face corresponds to an area surrounded by three or more edges.

[0137] Furthermore, a three-dimensional mesh has position information indicating the three-dimensional coordinate positions of vertices. The position information is also expressed as vertex information or geometry. A three-dimensional mesh also has connection information indicating the relationship between multiple vertices that make up an edge or a face. The connection information is also expressed as connectivity. A three-dimensional mesh also has attribute information indicating the attributes of the vertices, edges, or faces. The attribute information in a three-dimensional mesh is also expressed as texture.

[0138] For example, the attribute information may indicate the color, reflectance, or normal vector for a vertex, edge, or face. The direction of the normal vector may represent the front and back of the face.

[0139] The mesh data may be stored in a data file format such as an object file.

[0140] 16 is a conceptual diagram showing an example of a data file of mesh data according to this embodiment. In this example, the data file includes position information G(1) to G(N) of N vertices that make up the three-dimensional mesh, and attribute information A1(1) to A1(N) of the N vertices. Also, in this example, M pieces of attribute information A2(1) to A2(M) are included. The attribute information items do not need to correspond one-to-one to vertices or faces. Furthermore, attribute information need not exist.

[0141] The connection information is represented by a combination of vertex indices. n[1, 3, 4] indicates a triangular face formed by three vertices, n=1, n=3, and n=4. Also, m[2, 4, 6] indicates that the attribute information of m=2, m=4, and m=6 corresponds to the three vertices, respectively.

[0142] Furthermore, the actual contents of the attribute information may be written in a separate file. A pointer to that content may be associated with a vertex, a face, or the like. For example, attribute information indicating an image for a face may be stored in a two-dimensional attribute map file. The file name of the attribute map and two-dimensional coordinate values ​​in the attribute map may be written in attribute information A2(1) to A2(M). The method of specifying attribute information for a face is not limited to these methods, and any method may be used.

[0143] 17 is a conceptual diagram showing types of three-dimensional data according to this embodiment. Point cloud data and mesh data may represent static objects or dynamic objects. A static object is an object that does not change over time, and a dynamic object is an object that changes over time. A static object may correspond to three-dimensional data for any point in time.

[0144] For example, point cloud data for a given point in time may be referred to as a PCC frame, mesh data for a given point in time may be referred to as a mesh frame, and PCC frames and mesh frames may be simply referred to as frames.

[0145] The area of ​​the object may be limited to a certain range, as in normal video data, or may not be limited, as in map data. The density of points or surfaces may be determined in various ways. Sparse point cloud data or sparse mesh data may be used, or dense point cloud data or dense mesh data may be used.

[0146] Next, encoding and decoding of a point cloud or a three-dimensional mesh will be described. The device, process, or syntax for encoding and decoding vertex information of a three-dimensional mesh in the present disclosure may be applied to encoding and decoding of a point cloud. The device, process, or syntax for encoding and decoding of a point cloud in the present disclosure may be applied to encoding and decoding vertex information of a three-dimensional mesh.

[0147] Furthermore, a device, process, or syntax for encoding and decoding attribute information of a point cloud in the present disclosure may be applied to encoding and decoding connectivity information or attribute information of a three-dimensional mesh.Furthermore, a device, process, or syntax for encoding and decoding connectivity information or attribute information of a three-dimensional mesh in the present disclosure may be applied to encoding and decoding attribute information of a point cloud.

[0148] Furthermore, at least some of the processing may be shared between the encoding and decoding of point cloud data and the encoding and decoding of mesh data, thereby reducing the scale of the circuit and software program.

[0149] 18 is a block diagram showing an example configuration of a three-dimensional data encoder 113 according to this embodiment. In this example, the three-dimensional data encoder 113 includes a vertex information encoder 121, an attribute information encoder 122, a metadata encoder 123, and a multiplexer 124. The vertex information encoder 121, the attribute information encoder 122, and the multiplexer 124 may correspond to the vertex information encoder 101, the attribute information encoder 103, the post-processor 105, etc. in FIG.

[0150] In this example, the three-dimensional data encoder 113 encodes the three-dimensional data according to a geometry-based encoding method, which takes into account the three-dimensional structure. In addition, in the geometry-based encoding method, attribute information is encoded using configuration information obtained in encoding the vertex information.

[0151] Specifically, first, vertex information, attribute information, and metadata included in three-dimensional data generated from sensor data are input to a vertex information encoder 121, an attribute information encoder 122, and a metadata encoder 123, respectively. Here, connectivity information included in the three-dimensional data may be treated in the same way as attribute information. In addition, in the case of point cloud data, position information may be treated as vertex information.

[0152] The vertex information encoder 121 encodes the vertex information into compressed vertex information and outputs the compressed vertex information as encoded data to the multiplexer 124. The vertex information encoder 121 also generates metadata for the compressed vertex information and outputs it to the multiplexer 124. The vertex information encoder 121 also generates configuration information and outputs it to the attribute information encoder 122.

[0153] The attribute information encoder 122 uses the configuration information generated by the vertex information encoder 121 to encode the attribute information into compressed attribute information and outputs the compressed attribute information as encoded data to the multiplexer 124. The attribute information encoder 122 also generates metadata of the compressed attribute information and outputs it to the multiplexer 124.

[0154] The metadata encoder 123 encodes compressible metadata into compressed metadata and outputs the compressed metadata as encoded data to the multiplexer 124. The metadata encoded by the metadata encoder 123 may be used to encode vertex information and attribute information.

[0155] The multiplexer 124 multiplexes the compressed vertex information, the compressed vertex information metadata, the compressed attribute information, the compressed attribute information metadata, and the compressed metadata into a bitstream, and then inputs the bitstream to the system layer.

[0156] 19 is a block diagram showing an example configuration of a three-dimensional data decoder 213 according to this embodiment. In this example, the three-dimensional data decoder 213 includes a vertex information decoder 221, an attribute information decoder 222, a metadata decoder 223, and a demultiplexer 224. The vertex information decoder 221, the attribute information decoder 222, and the demultiplexer 224 may correspond to the vertex information decoder 201, the attribute information decoder 203, the preprocessor 204, and the like in FIG.

[0157] In this example, the three-dimensional data decoder 213 decodes three-dimensional data according to a geometry-based encoding method. The three-dimensional structure is taken into consideration in the decoding according to the geometry-based encoding method. Furthermore, in the decoding according to the geometry-based encoding method, attribute information is decoded using configuration information obtained in decoding vertex information.

[0158] Specifically, first, a bitstream is input from the system layer to a demultiplexer 224. The demultiplexer 224 separates compressed vertex information, compressed vertex information metadata, compressed attribute information, compressed attribute information metadata, and compressed metadata from the bitstream. The compressed vertex information and compressed vertex information metadata are input to a vertex information decoder 221. The compressed attribute information and compressed attribute information metadata are input to an attribute information decoder 222. The metadata is input to a metadata decoder 223.

[0159] The vertex information decoder 221 decodes vertex information from the compressed vertex information using metadata of the compressed vertex information. The vertex information decoder 221 also generates configuration information and outputs it to the attribute information decoder 222. The attribute information decoder 222 decodes attribute information from the compressed attribute information using the configuration information generated by the vertex information decoder 221 and the metadata of the compressed attribute information. The metadata decoder 223 decodes metadata from the compressed metadata. The metadata decoded by the metadata decoder 223 may be used to decode the vertex information and the attribute information.

[0160] Thereafter, the vertex information, attribute information, and metadata are output as three-dimensional data from the three-dimensional data decoder 213. Note that, for example, this metadata is metadata of the vertex information and attribute information, and can be used in an application program.

[0161] 20 is a block diagram showing another example configuration of the three-dimensional data encoder 113 according to the present embodiment. In this example, the three-dimensional data encoder 113 includes a vertex image generator 131, an attribute image generator 132, a metadata generator 133, a video encoder 134, a metadata encoder 123, and a multiplexer 124. The vertex image generator 131, the attribute image generator 132, and the video encoder 134 may correspond to the vertex information encoder 101 and the attribute information encoder 103 in FIG. 6 , etc.

[0162] In this example, the 3D data encoder 113 encodes the 3D data according to a video-based encoding method. In encoding according to the video-based encoding method, multiple 2D images are generated from the 3D data, and the multiple 2D images are encoded according to a video encoding method. Here, the video encoding method may be High Efficiency Video Coding (HEVC), Versatile Video Coding (VVC), or the like.

[0163] Specifically, first, vertex information and attribute information included in three-dimensional data generated from sensor data are input to a metadata generator 133. The vertex information and attribute information are then input to a vertex image generator 131 and an attribute image generator 132, respectively. The metadata included in the three-dimensional data is then input to a metadata encoder 123. Here, connectivity information included in the three-dimensional data may be treated in the same way as attribute information. In the case of point cloud data, position information may be treated as vertex information.

[0164] The metadata generator 133 generates map information of a plurality of two-dimensional images from the vertex information and attribute information, and inputs the map information to the vertex image generator 131, the attribute image generator 132, and the metadata encoder 123.

[0165] The vertex image generator 131 generates a vertex image based on the vertex information and map information, and inputs the generated image to the video encoder 134. The attribute image generator 132 generates an attribute image based on the attribute information and map information, and inputs the generated image to the video encoder 134.

[0166] The video encoder 134 encodes the vertex images and attribute images into compressed vertex information and compressed attribute information, respectively, in accordance with a video encoding method, and outputs the compressed vertex information and compressed attribute information as encoded data to the multiplexer 124. The video encoder 134 also generates metadata for the compressed vertex information and metadata for the compressed attribute information, and outputs them to the multiplexer 124.

[0167] The metadata encoder 123 encodes the compressible metadata into compressed metadata and outputs the compressed metadata as encoded data to the multiplexer 124. The compressible metadata includes map information. The metadata encoded by the metadata encoder 123 may also be used to encode vertex information and attribute information.

[0168] The multiplexer 124 multiplexes the compressed vertex information, the compressed vertex information metadata, the compressed attribute information, the compressed attribute information metadata, and the compressed metadata into a bitstream, and then inputs the bitstream to the system layer.

[0169] 21 is a block diagram showing another example configuration of the 3D data decoder 213 according to this embodiment. In this example, the 3D data decoder 213 includes a vertex information generator 231, an attribute information generator 232, a video decoder 234, a metadata decoder 223, and a demultiplexer 224. The vertex information generator 231, the attribute information generator 232, and the video decoder 234 may correspond to the vertex information decoder 201 and the attribute information decoder 203 in FIG. 8, etc.

[0170] In this example, the 3D data decoder 213 decodes the 3D data according to a video-based coding method. In the decoding according to the video-based coding method, a plurality of 2D images are decoded according to a video coding method, and 3D data is generated from the plurality of 2D images. Here, the video coding method may be High Efficiency Video Coding (HEVC), Versatile Video Coding (VVC), or the like.

[0171] Specifically, first, a bitstream is input from the system layer to the demultiplexer 224. The demultiplexer 224 separates compressed vertex information, compressed vertex information metadata, compressed attribute information, compressed attribute information metadata, and compressed metadata from the bitstream. The compressed vertex information, compressed vertex information metadata, compressed attribute information, and compressed attribute information metadata are input to the video decoder 234. The compressed metadata is input to the metadata decoder 223.

[0172] The video decoder 234 decodes the vertex images in accordance with the video encoding method. At this time, the video decoder 234 decodes the vertex images from the compressed vertex information using the metadata of the compressed vertex information. Then, the video decoder 234 inputs the vertex images to the vertex information generator 231. The video decoder 234 also decodes the attribute images in accordance with the video encoding method. At this time, the video decoder 234 decodes the attribute images from the compressed attribute information using the metadata of the compressed attribute information. Then, the video decoder 234 inputs the attribute images to the attribute information generator 232.

[0173] The metadata decoder 223 decodes metadata from the compressed metadata. The metadata decoded by the metadata decoder 223 includes map information used to generate vertex information and attribute information. The metadata decoded by the metadata decoder 223 may also be used to decode vertex images and attribute images.

[0174] The vertex information generator 231 reproduces vertex information from the vertex image in accordance with the map information included in the metadata decoded by the metadata decoder 223. The attribute information generator 232 reproduces attribute information from the attribute image in accordance with the map information included in the metadata decoded by the metadata decoder 223.

[0175] Thereafter, the vertex information, attribute information, and metadata are output as three-dimensional data from the three-dimensional data decoder 213. Note that, for example, this metadata is metadata of the vertex information and attribute information, and can be used in an application program.

[0176] Fig. 22 is a conceptual diagram showing a specific example of encoding processing according to this embodiment. Fig. 22 shows a three-dimensional data encoder 113 and a description encoder 148. In this example, the three-dimensional data encoder 113 includes a two-dimensional data encoder 141 and a mesh data encoder 142. The two-dimensional data encoder 141 includes a texture encoder 143. The mesh data encoder 142 includes a vertex information encoder 144 and a connection information encoder 145.

[0177] The vertex information encoder 144, the connection information encoder 145, and the texture encoder 143 may correspond to the vertex information encoder 101, the connection information encoder 102, and the attribute information encoder 103 in FIG.

[0178] For example, the two-dimensional data encoder 141 operates as a texture encoder 143 and generates a texture file by encoding the texture corresponding to the attribute information as two-dimensional data according to an image encoding method or a video encoding method.

[0179] The mesh data encoder 142 also operates as a vertex information encoder 144 and a connectivity information encoder 145, and generates a mesh file by encoding the vertex information and connectivity information. The mesh data encoder 142 may further encode mapping information for textures. The encoded mapping information may then be included in the mesh file.

[0180] The description encoder 148 also generates a description file by encoding a description corresponding to metadata such as text data. The description encoder 148 may encode the description at the system layer. For example, the description encoder 148 may be included in the system multiplexer 114 of FIG. 12 .

[0181] The above operations generate a bitstream containing texture files, mesh files, and description files, which may be multiplexed into the bitstream in file formats such as glTF (Graphics Language Transmission Format) or USD (Universal Scene Description).

[0182] The three-dimensional data encoder 113 may include two mesh data encoders as the mesh data encoder 142. For example, one mesh data encoder encodes vertex information and connectivity information of a static three-dimensional mesh, and the other mesh data encoder encodes vertex information and connectivity information of a dynamic three-dimensional mesh.

[0183] Correspondingly, two mesh files may then be included in the bitstream: for example, one mesh file corresponding to a static 3D mesh and another mesh file corresponding to a dynamic 3D mesh.

[0184] Furthermore, the static three-dimensional mesh may be a three-dimensional mesh of an intraframe coded using intraprediction, and the dynamic three-dimensional mesh may be a three-dimensional mesh of an interframe coded using interprediction. Furthermore, information on the dynamic three-dimensional mesh may be differential information between vertex information or connectivity information of the three-dimensional mesh of an intraframe and vertex information or connectivity information of the three-dimensional mesh of an interframe.

[0185] Fig. 23 is a conceptual diagram showing a specific example of the decoding process according to this embodiment. Fig. 23 shows a three-dimensional data decoder 213, a description decoder 248, and a renderer 247. In this example, the three-dimensional data decoder 213 includes a two-dimensional data decoder 241, a mesh data decoder 242, and a mesh reconstructor 246. The two-dimensional data decoder 241 includes a texture decoder 243. The mesh data decoder 242 includes a vertex information decoder 244 and a connectivity information decoder 245.

[0186] The vertex information decoder 244, the connection information decoder 245, the texture decoder 243, and the mesh reconstructor 246 may correspond to the vertex information decoder 201, the connection information decoder 202, the attribute information decoder 203, and the post-processor 205 in Fig. 8. The presenter 247 may correspond to the presenter 215 in Fig. 12.

[0187] For example, the two-dimensional data decoder 241 operates as a texture decoder 243, and decodes the texture corresponding to the attribute information from the texture file as two-dimensional data in accordance with an image coding method or a video coding method.

[0188] The mesh data decoder 242 also operates as a vertex information decoder 244 and a connectivity information decoder 245 to decode vertex information and connectivity information from the mesh file. The mesh data decoder 242 may further decode mapping information for textures from the mesh file.

[0189] The description decoder 248 also decodes descriptions corresponding to metadata such as text data from the description file. The description decoder 248 may decode the descriptions at the system layer. For example, the description decoder 248 may be included in the system demultiplexer 214 of FIG. 12 .

[0190] The mesh reconstructor 246 reconstructs a 3D mesh from the vertex information, connectivity information, and textures according to the description. The renderer 247 renders and outputs the 3D mesh according to the description.

[0191] Through the above operations, a 3D mesh is reconstructed and output from a bitstream containing a texture file, a mesh file, and a description file.

[0192] The three-dimensional data decoder 213 may include two mesh data decoders as the mesh data decoder 242. For example, one mesh data decoder decodes vertex information and connectivity information of a static three-dimensional mesh, and the other mesh data decoder decodes vertex information and connectivity information of a dynamic three-dimensional mesh.

[0193] Correspondingly, two mesh files may then be included in the bitstream: for example, one mesh file corresponding to a static 3D mesh and another mesh file corresponding to a dynamic 3D mesh.

[0194] Furthermore, the static three-dimensional mesh may be a three-dimensional mesh of an intraframe coded using intraprediction, and the dynamic three-dimensional mesh may be a three-dimensional mesh of an interframe coded using interprediction. Furthermore, information on the dynamic three-dimensional mesh may be differential information between vertex information or connectivity information of the three-dimensional mesh of an intraframe and vertex information or connectivity information of the three-dimensional mesh of an interframe.

[0195] A dynamic 3D mesh coding method is sometimes called DMC (Dynamic Mesh Coding), and a video-based dynamic 3D mesh coding method is sometimes called V-DMC (Video-based Dynamic Mesh Coding).

[0196] The point cloud encoding method is sometimes called PCC (Point Cloud Compression). The point cloud video-based encoding method is sometimes called V-PCC (Video-based Point Cloud Compression). The point cloud geometry-based encoding method is sometimes called G-PCC (Geometry-based Point Cloud Compression).

[0197] <Implementation Example> Fig. 24 is a block diagram showing an implementation example of the encoding device 100 according to this embodiment. The encoding device 100 includes a circuit 151 and a memory 152. For example, multiple components of the encoding device 100 shown in Fig. 5 etc. are implemented by the circuit 151 and memory 152 shown in Fig. 24.

[0198] The circuit 151 is a circuit that performs information processing and is a circuit that can access the memory 152. For example, the circuit 151 is a dedicated or general-purpose electric circuit that encodes a three-dimensional mesh. The circuit 151 may be a processor such as a CPU. Alternatively, the circuit 151 may be a collection of multiple electric circuits.

[0199] The memory 152 is a dedicated or general-purpose memory that stores information used by the circuit 151 to encode the three-dimensional mesh. The memory 152 may be an electric circuit and may be connected to the circuit 151. The memory 152 may also be included in the circuit 151. The memory 152 may also be a collection of multiple electric circuits. The memory 152 may also be a magnetic disk, an optical disk, or the like, and may also be expressed as a storage, a recording medium, or the like. The memory 152 may also be a non-volatile memory or a volatile memory.

[0200] For example, the memory 152 may store a three-dimensional mesh or a bitstream, or may store a program for the circuit 151 to encode the three-dimensional mesh.

[0201] Note that the encoding device 100 does not necessarily have to implement all of the components shown in Figure 5 and the like, and does not necessarily have to perform all of the processes shown here. Some of the components shown in Figure 5 and the like may be included in another device, and some of the processes shown here may be executed by another device. Furthermore, the encoding device 100 may implement any combination of the components of the present disclosure, and may perform any combination of the processes of the present disclosure.

[0202] Fig. 25 is a block diagram showing an example implementation of a decoding device 200 according to this embodiment. The decoding device 200 includes a circuit 251 and a memory 252. For example, multiple components of the decoding device 200 shown in Fig. 7 and other figures are implemented by the circuit 251 and memory 252 shown in Fig. 25.

[0203] The circuit 251 is a circuit that performs information processing and is a circuit that can access the memory 252. For example, the circuit 251 is a dedicated or general-purpose electric circuit that decodes a three-dimensional mesh. The circuit 251 may be a processor such as a CPU. Alternatively, the circuit 251 may be a collection of multiple electric circuits.

[0204] The memory 252 is a dedicated or general-purpose memory that stores information for the circuit 251 to decode the 3D mesh. The memory 252 may be an electric circuit and may be connected to the circuit 251. The memory 252 may also be included in the circuit 251. The memory 252 may also be a collection of multiple electric circuits. The memory 252 may also be a magnetic disk, an optical disk, or the like, and may also be expressed as a storage, a recording medium, or the like. The memory 252 may also be a non-volatile memory or a volatile memory.

[0205] For example, the memory 252 may store a three-dimensional mesh or a bitstream, or may store a program for the circuit 251 to decode the three-dimensional mesh.

[0206] Note that the decoding device 200 does not necessarily have to implement all of the components shown in Figure 7 and the like, and does not necessarily have to perform all of the processes shown here. Some of the components shown in Figure 7 and the like may be included in another device, and some of the processes shown here may be executed by another device. Furthermore, the decoding device 200 may implement any combination of the components of the present disclosure, and may perform any combination of the processes of the present disclosure.

[0207] The encoding method and the decoding method including the steps performed by each component of the encoding device 100 and the decoding device 200 of the present disclosure may be executed by any device or system. For example, part or all of the encoding method and the decoding method may be executed by a computer including a processor, a memory, an input / output circuit, etc. In this case, the encoding method and the decoding method may be executed by the computer executing a program for causing the computer to execute the encoding method and the decoding method.

[0208] Alternatively, the program or the bitstream may be recorded on a non-transitory computer-readable recording medium such as a CD-ROM.

[0209] An example of a program may be a bitstream. For example, a bitstream including an encoded three-dimensional mesh includes syntax elements for causing the decoding device 200 to decode the three-dimensional mesh. The bitstream then causes the decoding device 200 to decode the three-dimensional mesh according to the syntax elements included in the bitstream. Thus, the bitstream may play a role similar to that of a program.

[0210] The bitstream may be an encoded bitstream containing the encoded 3D mesh, or may be a multiplexed bitstream containing the encoded 3D mesh and other information.

[0211] Furthermore, each component of the encoding device 100 and the decoding device 200 may be configured with dedicated hardware, general-purpose hardware that executes the above-mentioned programs, or a combination of these. The general-purpose hardware may be configured with a memory in which the programs are recorded and a general-purpose processor that reads and executes the programs from the memory. Here, the memory may be a semiconductor memory or a hard disk, and the general-purpose processor may be a CPU.

[0212] Furthermore, the dedicated hardware may be configured with a memory, a dedicated processor, etc. For example, the dedicated processor may execute the encoding method and the decoding method by referring to a memory for recording data.

[0213] Furthermore, as described above, each component of the encoding device 100 and the decoding device 200 may be an electric circuit. These electric circuits may form a single electric circuit as a whole, or each may be a separate electric circuit. Furthermore, these electric circuits may correspond to dedicated hardware, or may correspond to general-purpose hardware that executes the above-mentioned programs, etc. Furthermore, the encoding device 100 and the decoding device 200 may be implemented as an integrated circuit.

[0214] Furthermore, the encoding device 100 may be a transmitting device that transmits the three-dimensional mesh, and the decoding device 200 may be a receiving device that receives the three-dimensional mesh.

[0215] Displacement Encoding and Decoding The following terminology is used here by way of example:

[0216] (1) Image An image is a data unit made up of a set of pixels, and includes a picture or a block smaller than a picture. Images include both moving images and still images.

[0217] (2) Picture A picture is a unit of image processing that is made up of a set of pixels, and is also called a frame or field.

[0218] (3) Block A block is a processing unit consisting of a specific number of pixels. The term shown in the following example is also used for a block. The shape of a block is not particularly limited. A block may be, for example, a rectangular shape of M×N pixels or a square shape of M×M pixels. A block may also be a triangular shape, a circular shape, or another shape. Examples of blocks are as follows:

[0219] Slice, tile, or brick CTU, superblock, or basic division unit VPDU, processing division unit for hardware CU, processing block unit, prediction block unit (PU), or orthogonal transform block unit (TU) Sub-block

[0220] (4) Pixel or Sample A pixel or sample is the smallest point of an image, in other words, the smallest unit. Pixels or samples include not only pixels at integer positions, but also pixels at sub-pixel positions generated based on pixels at integer positions.

[0221] (5) Pixel Value or Sample Value: A pixel value or sample value is a unique value of a pixel. The pixel value or sample value may include a luma value, a chroma value, or an RGB gradation level, and may also include a depth value or a binary value of 0 or 1.

[0222] (6) Flags A flag indicates one or more bits. A flag is, for example, a parameter or index represented by two or more bits. A flag may indicate not only a value represented by a binary number, but also a value represented by a number other than a binary number.

[0223] (7) Signal: A signal is something that is symbolized or coded to transmit information. A signal includes a discrete digital signal or a continuous analog signal.

[0224] (8) Stream or Bit Stream A stream or bit stream is a digital data sequence that indicates the flow of digital data. A stream or bit stream may be a single stream, or may be configured to include multiple streams with multiple layers. A stream or bit stream may be transmitted by serial communication using a single transmission path, or may be transmitted by packet communication using multiple transmission paths.

[0225] (9) Difference: For scalar quantities, difference can include simple difference (x - y) and difference calculations, such as absolute difference (|x - y|), squared difference (x^2 - y^2), square root difference (√(x - y)), weighted difference (ax - b, where a and b are constants), or offset difference (x - y + a, where a is an offset).

[0226] (10) Sum. For scalar quantities, sums can include simple sum (x + y) and addition operations. Sum can also include absolute sum (|x + y|), sum of squares (x^2 + y^2), square root of sum (√(x + y)), weighted sum (ax + by, where a and b are constants), or offset sum (x + y + a, where a is an offset).

[0227] (11) "Based on" The expression "based on something" means that something other than that "something" may be taken into consideration. Also, "based on" can be used both when a direct result is obtained and when a result is obtained through an intermediate result.

[0228] (12) "Used" or "Using" The phrases "something was used" or "used something" mean that something other than the "something" may be taken into consideration. The phrases "used" or "used" may be used both in cases where a direct result is obtained and in cases where a result is obtained via an intermediate result.

[0229] (13) Prohibition "Prohibit" can be rephrased as "not permitted." Also, "not prohibited / prohibited" or "permitted / permitted" does not necessarily mean "obligation."

[0230] (14) "Restriction" or "Limitation" "Restriction" or "Limitation" can be rephrased as "not permitted / not allowed" or "not permitted / permitted." Furthermore, "prohibited / not prohibited" or "not permitted / permitted" does not necessarily mean "obligation." Furthermore, what is prohibited quantitatively or qualitatively may be either partial or total.

[0231] (15) Chroma The term chroma is an adjective, represented by the symbols Cb or Cr, that indicates that a sample array or a single sample represents one of the two color-difference signals associated with a primary color. The term chroma is sometimes used instead of the term chrominance.

[0232] (16) Luma The term luma is an adjective, represented by the symbols or subscripts Y or L, that indicates that a sample array or a single sample represents a monochrome signal for a primary color. The term luma is sometimes used instead of the term luminance.

[0233] The encoding / decoding system of this embodiment will be described below.

[0234] A typical three-dimensional model (also called a 3D model) digitally represents an object so that a user can explore the model using zoom, pan, and rotation in all three dimensions while it is rendered over time. One way to construct such a representation is to build a 3D mesh using triangles. The model stores the positions of the triangle vertices, their connectivity to each other, and their associated attributes (such as normals or UV patches).

[0235] Storing all this information in uncompressed form requires a very large storage space and therefore a very large bandwidth for transmission. The triangles that form the mesh often have repeating patterns and similar properties, especially in temporal and spatial neighborhoods. These repetitions can be exploited to develop efficient encoding and decoding methods for storage and transmission. One such encoding and decoding method is Video-based Dynamic Mesh Coding (V-DMC).

[0236] 26 is a block diagram showing another example of the configuration of the encoding / decoding system according to this embodiment. As shown in FIG. 26, the encoding / decoding system includes an encoding device 100 and a decoding device 200.

[0237] The encoding / decoding system accepts input three-dimensional meshes (also called 3D meshes) in the form of three-dimensional coordinates of vertices (vertex information), connectivity (connection information) and associated attributes (attribute information), which may include texture maps as well as geometry.

[0238] The encoding device 100 takes an input 3D mesh (also referred to as an input 3D mesh or input mesh) in the form of three-dimensional coordinates of vertices, connectivity, and associated attributes. The encoding device 100 encodes all associated information into a stream. The stream may consist of a single bitstream or multiple bitstreams.

[0239] The network 300 transmits the stream generated by the encoding device to the decoding device 200. The network 300 may be the Internet, a wide area network (WAN), a local area network (LAN), or any combination thereof. Furthermore, the network 300 is not necessarily limited to a two-way communication network, but may also be a one-way communication network that transmits broadcast waves such as terrestrial digital broadcasting or satellite broadcasting. Instead of the network 300, a recording medium such as a digital versatile disc (DVD) or a blue-ray disc (BD) on which a stream is recorded may be used.

[0240] The stream is transmitted to a decoding device 200 via a network 300. The decoding device 200 decodes the bitstream and generates a 3D mesh using the 3D coordinates, connectivity, and associated attributes of the decoded vertices. The decoding device 200 outputs the generated 3D mesh (also referred to as an output 3D mesh or output mesh).

[0241] FIG. 27 is a diagram showing another example of the configuration of the encoding device 100.

[0242] As shown in FIG. 27, the encoding device 100 includes a preprocessor 1103 and a compressor 1106 .

[0243] The encoding device 100 reads an input mesh 1101 and an attribute map 1102 and passes them to a preprocessor 1103. The preprocessor 1103 processes the input mesh to extract a base mesh 1104 and displacement data 1105. The attribute map 1102, along with the extracted base mesh 1104 and displacement data 1105, are passed to a compressor 1106.

[0244] The compressor 1106 also compresses the base mesh 1104, the displacement data 1105, and the attribute map 1102 to generate a bitstream 1107. The compressor 1106 can transmit additional information to the decoding device 200 by further including metadata 1108 in the bitstream 1107.

[0245] FIG. 28 is a diagram showing another example of the configuration of the decoding device 200.

[0246] As shown in FIG. 28, the decoding device 200 includes a decompressor 2102 and a post-processor 2106 .

[0247] The decoding device 200 reads a bitstream 2101 and passes it to a decompressor 2102. The decompressor 2102 decompresses a base mesh 2103, displacement data 2104, and an attribute map 2108 from the bitstream 2101 and passes them to a post-processor 2106. An example of the displacement data 2104 is a displacement vector.

[0248] The post-processor 2106 also processes the base mesh 2103 according to the displacement data 2104 and the attribute map 2108 to generate an output mesh 2107. The post-processor 2106 may further use information from the metadata 2105 to generate the output mesh 2107.

[0249] FIG. 29 is a block diagram showing yet another example configuration of the encoding device 100 according to this embodiment.

[0250] In this example, the encoding device 100 comprises a volumetric capturer 511, a projector 512, a base mesh encoder 513, a displacement encoder 514, an attribute encoder 515, and optionally one or more other type encoders 516.

[0251] The volumetric capturer 511 captures content and outputs the captured content to the projector 512 .

[0252] The projector 512 projects the content onto a 3D mesh frame containing vertex geometry coordinates, texture coordinates, and connectivity data. The data is output to a base mesh encoder 513, a displacement encoder 514, an attribute encoder 515, and optionally one or more other type encoders 516. Each encoder compresses the data into a bitstream.

[0253] FIG. 30 is a block diagram showing yet another example configuration of the decoding device 200 according to this embodiment.

[0254] In this example, the decoding device 200 comprises a base mesh decoder 613 , a displacement decoder 614 , an attribute decoder 615 , one or more other type decoders 616 , and a 3D reconstructor 617 .

[0255] The bitstream is sent to a base mesh decoder 613, a displacement decoder 614, an attribute decoder 615, and optionally one or more other type decoders 616. These decoders decode the bitstream to generate decoded data including vertex geometry coordinates, texture coordinates, and connectivity data. The decoded data is then sent to a 3D reconstructor 617, which reconstructs a 3D mesh frame.

[0256] The encoding process performed by the encoding device 100 will be described in detail below.

[0257] Fig. 31 is a flow diagram showing the processing of the encoding device 100. Fig. 32 is an explanatory diagram conceptually showing the encoding of mesh frames. The processing of the encoding device 100 will be described with reference to Figs. 31 and 32.

[0258] In step S101, the encoding device 100 reads a 3D mesh frame, which is an input mesh frame, and its attributes. The input mesh frame is a mesh frame input to the encoding device 100. An example of the 3D mesh frame that is an input mesh frame is shown as mesh frame 1301 (see FIG. 32 ).

[0259] In step S102, the encoding device 100 performs a decimation process on the input mesh frame read in step S101 to generate a base mesh frame having fewer vertices than the input mesh frame. The base mesh frame generated by decimating the mesh frame 1301 is shown as a base mesh frame 1302 (see FIG. 32).

[0260] In step S103, the encoding device 100 calculates displacement information that the decoding device 200 uses to reconstruct a mesh frame. The displacement information corresponds to a displacement vector directed from a vertex of the base mesh frame generated in step S102 to a vertex of the input mesh frame. One method for calculating the displacement information is to subtract the coordinates of the vertex of the base mesh frame from the coordinates of the vertex of the input mesh frame. The displacement information calculated from the mesh frame 1301 and the base mesh frame 1302 is shown as displacement information 1303 (see FIG. 32). The displacement information 1303 is in vector format, in other words, expressed as a displacement vector.

[0261] In step S104, the encoding device 100 encodes the base mesh frame generated in step S102, the displacement information generated in step S103, and the attributes of the input mesh frame into a bitstream (corresponding to a compressed bitstream). An example of the bitstream is shown as bitstream 1304 (see FIG. 32).

[0262] Specifically, the bitstream 1304 includes vertex coordinates and connectivity information for vertices A, C, E, and F, displacement information, a video bitstream including texture data, and a compressed attribute map (see FIG. 32). The displacement information includes displacement information for displacing vertices based on vertex coordinates obtained from the subdivided base mesh frame. The compressed attribute map is texture coordinates for applying texture data to a mesh frame reconstructed using the base mesh frame and the displacement information.

[0263] The decoding process performed by the decoding device 200 will be described in detail below.

[0264] Fig. 33 is a flow diagram showing the processing of the decoding device 200. Fig. 34 is an explanatory diagram conceptually showing the decoding of a 3D mesh. The processing of the decoding device 200 will be described with reference to Figs. 33 and 34.

[0265] In step S201, the decoding device 200 decodes a base mesh frame and attributes from a bitstream (corresponding to a compressed bitstream). An example of the decoded base mesh frame (corresponding to a decoded base mesh frame) is shown as a decoded base mesh frame 2301 (see FIG. 34).

[0266] In step S202, the decoding device 200 generates subdivided vertices by performing a subdivision process on the base mesh frame decoded in step S201. An example of a base mesh frame including subdivided vertices is shown as base mesh frame 2302 (see FIG. 34).

[0267] In step S203, the decoding device 200 decodes the disparity information from the bitstream (corresponding to the compressed bitstream). An example of the decoded disparity information is shown as disparity information 2303 (see FIG. 34). The disparity information 2303 is in vector format, in other words, expressed as a disparity vector.

[0268] In step S204, the decoding device 200 reconstructs the shape of the mesh frame by moving the vertices of the base mesh frame, including the subdivided vertices, to new positions using the displacement information, and then restores the mesh frame by applying attribute information. An example of the attribute is texture. An example of the reconstructed mesh frame is shown as mesh frame 2304 (see FIG. 34 ).

[0269] FIG. 35 is a block diagram showing an example of the configuration of a decoding device according to this embodiment.

[0270] FIG. 35 shows an example of a block diagram of a general intra-decoding system.

[0271] The decoding device shown in FIG. 35 comprises a demultiplexer 1231, a switch 1232, a static mesh decoder 1233, a mesh buffer 1234, a motion decoder 1235, a base mesh reconstructor 1236, an inverse quantizer 1237, a video decoder 1238, an image unpacker 1239, an inverse quantizer 1240, an inverse wavelet transformer 1241, a reconstructor 1242, a video decoder 1243, and a color converter 1244.

[0272] The demultiplexer 1231 receives the compressed bitstream and separates it into compressed data for the base mesh, video containing displacement data (also called displacement bitstream), and video containing attribute data (also called attribute bitstream). The compressed data for the base mesh is passed to a switch 1232. The switch 1232 determines whether to perform intra-decoding or inter-decoding based on parameters in the bitstream.

[0273] If an intra-decoding process is selected, the bitstream is passed to a static mesh decoder 1233, which generates a quantized base mesh. The static mesh decoder 1233 is, for example, a decoder that uses an edge breaker algorithm to decode 3D mesh data. The static mesh decoder 1233 generates a quantized base mesh from the bitstream. The quantized base mesh generated by the static mesh decoder 1233 is stored in a mesh buffer 1234 for reference when an inter-decoding process is selected.

[0274] If inter-decoding is selected, switch 1232 passes compressed data for the base mesh to motion decoder 1235. Motion decoder 1235 receives a previously decoded quantized base mesh and decodes motion data representing the differences in vertex coordinates between the quantized base mesh stored in mesh buffer 1234 and the current quantized base mesh. The motion data and the quantized base mesh stored in mesh buffer 1234 are used by base mesh reconstructor 1236 to reconstruct the current quantized base mesh. The quantized base mesh resulting from either inter-decoding or intra-decoding is passed to inverse quantizer 1237 to obtain a decoded base mesh.

[0275] The video containing the displacement data is passed to a video decoder 1238, since the bitstream contains the displacement data in an image format with two chroma information and one luma information. The video decoder 1238 decodes the data using a video frame decompression method. Alternatively, the displacement data can be decoded using an arithmetic decoder. This decompressed data is passed to an image unpacker 1239, which extracts wavelet coefficients associated with each vertex from the image-format decompressed data. An inverse quantizer 1240 dequantizes the quantized wavelet coefficients into the three components associated with each vertex. An inverse wavelet transformer 1241 inversely transforms the result to finally obtain decoded displacement data. The decoded displacement data and the decoded base mesh are passed to a reconstructor 1242, which performs edge refinement on the decoded base mesh and displaces the vertices using the decoded displacement data to obtain a decoded mesh.

[0276] The video containing the attribute data is passed to another video decoder 1243 to obtain a decoded attribute bitstream, which is further processed in a color converter 1244 for color space and color format conversion to obtain a decoded attribute map.

[0277] FIG. 36 is a block diagram showing an example of the configuration of a decoding device according to this embodiment.

[0278] FIG. 36 illustrates an example of a reconstructor that obtains a decoded 3D mesh 1256 from a decoded base mesh 1251 and decoded displacement data 1254.

[0279] The decoded base mesh 1251 is passed to a subdivider 1252 .

[0280] The subdivision unit 1252 subdivides any two connected vertices in the entire 3D mesh by adding a new vertex between them. This process can be repeated several times to include vertices created in previous subdivision steps to generate a predefined number of vertices. Each subdivision iteration across the 3D mesh generates a new level of detail (LoD). The subdivided mesh 1253 and the decoded displacement data 1254 are passed to a displacer 1255. The displacer 1255 generates a decoded 3D mesh 1256 by moving each vertex to a new position according to the corresponding displacement data.

[0281] The subdivision is described below and is performed by a subdivider (specifically subdivider 1206 or subdivider 2204).

[0282] FIG. 37 is an explanatory diagram showing an example of subdivision.

[0283] The base mesh shown in FIG. 37(a) includes vertices A, B, and C and connectivity information indicating their connectivity.

[0284] 37(b) shows a mesh generated by the first subdivision, in other words, the mesh after the first subdivision. In the first subdivision, the subdivider generates vertices D, E, and F and connectivity information indicating their connectivity. The mesh generated by the subdivider is also referred to as LoD1 or first LoD.

[0285] Vertex D of the mesh after the first subdivision is a vertex generated by subdivision based on vertices A and B. Similarly, vertex E is a vertex generated by subdivision based on vertices B and C. Vertex F is a vertex generated by subdivision based on vertices A and C.

[0286] As an example, vertex D may be the midpoint of line segment AB (in other words, side AB) connecting vertices A and B that were the basis for its generation. Similarly, vertex E may be the midpoint of line segment AC. Vertex F may be the midpoint of line segment BC.

[0287] 37(c) shows the mesh generated by the second subdivision, i.e., the mesh after the second subdivision. In the second subdivision, the subdivider generates vertices G, H, I, J, K, L, M, N, and O and connectivity information indicating their connectivity. The mesh generated by the subdivider is also called LoD2 or second LoD.

[0288] Vertex G of the mesh after the second subdivision is a vertex generated by subdivision based on vertices A and D. Similarly, vertex H is a vertex generated by subdivision based on vertices A and E. Vertex I is a vertex generated by subdivision based on vertices B and D. Vertex J is a vertex generated by subdivision based on vertices D and F. Vertex K is a vertex generated by subdivision based on vertices E and F. Vertex L is a vertex generated by subdivision based on vertices C and E. Vertex M is a vertex generated by subdivision based on vertices B and F. Vertex N is a vertex generated by subdivision based on vertices C and F. Vertex O is a vertex generated by subdivision based on vertices D and E.

[0289] As an example, vertex G may be the midpoint of line segment AD (in other words, side AD) connecting vertices A and D, which were the source of its generation. Similarly, vertex H may be the midpoint of line segment AE. vertex I may be the midpoint of line segment BD. vertex J may be the midpoint of line segment DF. vertex K may be the midpoint of line segment EF. vertex L may be the midpoint of line segment CE. vertex M may be the midpoint of line segment BF. vertex N may be the midpoint of line segment CF. vertex O may be the midpoint of line segment DE.

[0290] The displacement of vertices will be described below with reference to Figures 38 and 39. The displacement of vertices is performed by the reconstructor 2209.

[0291] Fig. 38 is an explanatory diagram showing an example of displacement of vertices after subdivision, and Fig. 39 is an explanatory diagram showing an example of vertices of an original mesh.

[0292] The base mesh shown in FIG. 38(a) includes vertices A, B, C, and Z and connectivity information indicating their connectivity.

[0293] 38(b) shows a mesh generated by the first subdivision, in other words, a mesh after the first subdivision (i.e., the first LoD). In the first subdivision, the subdivider generates vertices S, T, U, X, or Y and connectivity information indicating their connectivity. The vertices S, T, U, X, or Y are similar to the vertices D, E, and F shown in FIG. 37(b).

[0294] 38(c) shows a mesh generated by the second subdivision, in other words, a mesh after the second subdivision (i.e., the second LoD). In the second subdivision, the subdivider generates vertices D, E, F, G, and H and connectivity information indicating their connectivity. Vertices D, E, F, G, and H are the same as vertices G, H, I, J, K, L, M, N, and O shown in FIG. 37(c).

[0295] Figure 38(d) shows a mesh including the vertices after they have been displaced after subdivision, with vertices A, B, C, D, E, F, G, H, S, T, U, X, Y, and Z shown in Figure 38(d) being located at positions displaced using displacement information from the positions of the vertices shown in Figure 38(c).

[0296] The original mesh shown in FIG. 39 is an example of the mesh input to the encoding device 100, that is, the mesh before encoding.

[0297] The mesh shown in Fig. 38 has a shape similar to that of the original mesh shown in Fig. 39. The displacement information is generated by the displacement vector calculator 1207 of the encoding device 100 as information indicating the displacement from the vertices of the base mesh to the vertices of the original mesh, and therefore, by reconstructing the mesh using the displacement information thus generated, a mesh having a shape similar to that of the original mesh is generated.

[0298] The decoding device 200 can output the mesh shown in FIG.

[0299] Next, the division of a mesh into sub-meshes will be described with reference to FIGS.

[0300] A mesh can be divided into smaller parts and coded separately, with the vertices of the mesh being divided in such a way that the coordinates and connectivity of the vertices in each part can be coded independently.

[0301] Fig. 40 is an explanatory diagram showing an example of a mesh, and Fig. 41 is an explanatory diagram showing an example of dividing a mesh into sub-meshes.

[0302] The mesh shown in FIG. 40 is the original mesh, which is sometimes called a full mesh in contrast to a sub-mesh.

[0303] Figure 41 shows how the full mesh shown in Figure 40 is divided into two sub-meshes. For vertices A, B, and C of the full mesh (see Figure 40), vertex A is duplicated to vertices A1 and A2, vertex B is duplicated to vertices B1 and B2, and vertex C is duplicated to vertices C1 and C2, thereby creating two sub-meshes (i.e., a first sub-mesh and a second sub-mesh) from the full mesh. The first sub-mesh and the second sub-mesh are each independently decodable meshes.

[0304] Packing of displacement information into image frames will be described below with reference to FIGS.

[0305] 42, 43 and 44 are explanatory diagrams showing examples of packing of displacement information into image frames. Note that image frames can also be called video frames.

[0306] The vertex displacement data is encoded as image frame data by being mapped to each component of a YUV format image frame (i.e., each of the Y component (Y Plane), U component (U Plane), and V component (V Plane)). This case will be described below as an example. As another example, the vertex displacement data may be encoded as image frame data by being mapped to each component of an RGB format image frame (each of the R component, G component, and B component).

[0307] The decoding device 200 can use an image encoding module to extract the displacement data. The displacement data can be in the form of X, Y, or Z components in a global coordinate system (e.g., a Cartesian coordinate system), or normal, tangential, or both tangential components in a local coordinate system. Methods for mapping the displacement data to an image frame include the following:

[0308] For example, in the first method, the displacement data is arranged in the image frame in scan order, and an example of packing the displacement data in this case is shown in Figure 42. The displacement data is directly mapped onto the image frame according to a predefined scan order.

[0309] Note that since an image frame has a fixed height and width, it may happen that the displacement data does not fit perfectly in the frame, in which case the remaining part of the image frame is padded with padding data (see Figure 42).

[0310] For example, in the second method, the displacement data is separated into multiple LoDs and mapped to the Y, U, and V components of the image frame. An example of packing of the displacement data in this case is shown in Figure 43. Here, the displacement data of the image frame of the next LoD starts immediately after the displacement data of the previous LoD ends. As in the first method, if the displacement data does not fit exactly into the image frame, padding is performed at the end of the image frame (see Figure 43).

[0311] For example, in the third method, displacement data corresponding to the LoD is mapped to the Y component, U component, and V component of the image frame in a manner different from that in the second method. An example of packing of the displacement data in this case is shown in Figure 44. In this way, each LoD can be decoded independently. In the third method, middle padding is performed on the displacement data of each LoD, and CTU alignment is performed together with padding at the end of the video frame (see Figure 44).

[0312] <Other Examples> Although the aspects of the encoding device and the decoding device have been described above according to the embodiments, the aspects of the encoding device and the decoding device are not limited to the embodiments. Modifications that a person skilled in the art can conceive of may be applied to the embodiments, and multiple components in the embodiments may be combined in any manner.

[0313] For example, a process performed by a specific component in the embodiment may be performed by another component instead of the specific component. Also, the order of multiple processes may be changed, or multiple processes may be performed in parallel.

[0314] Furthermore, as described above, at least some of the configurations of the present disclosure may be implemented as an integrated circuit. At least some of the processes of the present disclosure may be used as an encoding method or a decoding method. A program for causing a computer to execute the encoding method or the decoding method may be used. A non-transitory computer-readable recording medium on which the program is recorded may be used. A bitstream for causing a decoding device to perform a decoding process may be used.

[0315] Furthermore, at least some of the configurations and processes of the present disclosure may be used as a transmitting device, a receiving device, a transmitting method, or a receiving method. A program for causing a computer to execute the transmitting method or the receiving method may be used. Furthermore, a non-transitory computer-readable recording medium on which the program is recorded may be used.

[0316] In the above embodiments, each component may be configured with dedicated hardware, or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory. Here, the software that realizes the encoding device and the like in the above embodiments is the following program.

[0317] In other words, the software is a program that causes a computer to execute an encoding method that obtains a first frame to be encoded, encodes first data having one or more layers contained in the first frame by referencing second data having one or more layers contained in a second frame, and when encoding the first data, determines one of a plurality of processes for each of the one or more layers contained in the first data using a value indicating the layer and a value related to the one or more layers contained in the second data, and executes the determined one process on the first data of that layer.

[0318] The software for realizing the decoding device and the like according to the above-described embodiment is the following program.

[0319] In other words, the software is a program that causes a computer to execute a decoding method in which it obtains a first frame to be decoded, decodes first data having one or more layers contained in the first frame by referring to second data having one or more layers contained in a second frame, and when decoding the first data, determines one of a plurality of processes for each of the one or more layers contained in the first data using a value indicating the layer and a value related to the one or more layers contained in the second data, and executes the determined one process on the first data of that layer.

[0320] Next, the configuration of an encoding device when a mesh is divided into a plurality of sub-meshes will be described.

[0321] Fig. 45 is a diagram showing an example of the configuration of an encoding device when dividing into a plurality of sub-meshes. Fig. 45 is a diagram showing an example of the configuration of a pre-processor.

[0322] An input mesh 1401 is divided into a plurality of sub-meshes 1402. The input mesh 1401 is, for example, a full mesh. Each of the sub-meshes 1402 is input to an encoding device 1400 shown in FIG. 45 . That is, the encoding process by the encoding device 1400 is performed after the input mesh 1401 is divided into the plurality of sub-meshes 1402.

[0323] As shown in FIG. 45, the encoding device 1400 includes a preprocessor 1404 and a compressor 1408 .

[0324] The encoding device 1400 reads one of the submeshes 1402 that corresponds to the encoding device 1400 and an attribute map 1403, and passes them to a preprocessor 1404. The preprocessor 1404 processes the submesh 1402 to extract a base mesh 1405 and displacement data 1406.

[0325] As shown in FIG. 46, the preprocessor 1404 includes a base mesh generator 1411 , a subdivision unit 1412 , and a displacement generator 1413 .

[0326] The base mesh generator 1411 generates a base mesh based on the mesh or sub-mesh 1402 .

[0327] The subdivision unit 1412 subdivides the base mesh using a predetermined method to generate a subdivided mesh (Subdivided Mesh, Subdivided Base Mesh).

[0328] The displacement generator 1413 generates displacement data 1406 based on the subdivided mesh and the submesh 1402. The displacement data is, for example, a difference vector between the input mesh (submesh 1402) and the subdivided mesh.

[0329] Note that the decoding device also uses the same subdivision method as that used in the encoding device 1400. The subdivision method or parameters used in the encoding device 1400 may be transmitted to the decoding device 1420. That is, the subdivision method or parameters may be included in the bitstream.

[0330] The attribute map 1403 is passed to a compressor 1408 along with a base mesh 1405 and displacement data 1406 generated by a preprocessor 1404 .

[0331] The compressor 1408 compresses the base mesh 1405, the displacement data 1406, and the attribute map 1403 to generate a bitstream 1409. The compressor 1408 can also include metadata 1407 in the bitstream 1409 to transmit additional information to the decoder 1420.

[0332] Next, the configuration of the decoding device when divided into a plurality of sub-meshes will be described.

[0333] FIG. 47 is a diagram showing an example of the configuration of a decoding device when divided into a plurality of sub-meshes.

[0334] As shown in FIG. 47, the decoding device 1420 includes a decompressor 1422 and a post-processor 1427 .

[0335] The decoder 1420 reads the bitstream 1421 and passes it to the decompressor 1422. The decompressor 1422 decompresses the base mesh 1423, the displacement data 1424, and the attribute map 1426 from the bitstream 1421 and passes them to the post-processor 1427. An example of the displacement data 1424 is a displacement vector.

[0336] Additionally, a post-processor 1427 processes the base mesh 1423 according to the displacement data 1424 and the attribute map 1426 to generate a merged sub-mesh 1428. The post-processor 1427 may further use information from the metadata 1425 to generate the merged sub-mesh 1428.

[0337] The post-processor 1427 reconstructs the deformed mesh (subdivision, displacement unit). In the subdivision, the post-processor 1427 subdivides the base mesh for each decoded sub-mesh, adds a displacement vector to the subdivided base mesh, and restores the sub-mesh. That is, the post-processor 1427 processes the reconstructed deformed mesh for each sub-mesh. The restored sub-meshes are merged to reconstruct the mesh before division.

[0338] FIG. 48 is a diagram illustrating post-decoding processing.

[0339] The decoder 1432 acquires the bitstream 1431 and performs a decoding process. After the decoding process, a post-decoding unit 1433 may perform a process.

[0340] The processing in the post-decoding unit 1433 is optional depending on the application. The post-decoding unit 1433 converts the decoded data into a nominal format, such as video conversion from YUV space to RGB space. The post-decoding unit 1433 includes a pre-reconstruction unit 1434, a reconstruction unit 1435, a post-reconstruction unit 1436, and an adaptation unit 1437. In other words, post-decoding encapsulates multiple processes performed by the pre-reconstruction unit 1434, the reconstruction unit 1435, the post-reconstruction unit 1436, and the adaptation unit 1437.

[0341] The pre-reconstructor 1434 scales the normalized texture coordinates to match the dimensions of the texture image, for example, in the context of video-based dynamic mesh coding.

[0342] The reconstructor 1435 performs a reconstruction process, for example, on the decoded atlas frames, the decoded base mesh frames, the decoded video frames, and syntax elements associated with the same mesh sequence, the output of which is a sequence of reconstructed mesh frames prior to a post-reconstruction step.

[0343] In the context of video-based dynamic mesh coding, the post-reconstructor 1436 may, for example, perform a number of smoothing operations on the reconstructed mesh frames, including collapsing edges or adding new vertices.

[0344] The adaptation unit 1437 is applied by some application to adapt the reconstructed mesh to a given scenario, for example, the vertices of the reconstructed mesh are transformed from the 3D model coordinate system to the 3D world coordinate system.

[0345] Fig. 49 is a flowchart showing an example of a decoding process for a three-dimensional mesh. Fig. 50 is a diagram showing an example of different two-dimensional surfaces. Figs. 51 and 52 are diagrams showing an example of three-dimensionally rotating a set of vertex coordinates around the z-axis. Fig. 53 is a diagram showing an example of projecting vertex coordinates onto a two-dimensional surface. Fig. 54 is a diagram showing an example of Apple scaling a set of two-dimensional coordinates. Note that in Fig. 50, the mesh has two-dimensional planes A to F.

[0346] The decoding device 1420 decodes a set of vertex coordinates 1500 from the bitstream (S1501). This set of vertex coordinates is the three-dimensional coordinates of a mesh, and is obtained by converting the set of vertex coordinates expressed in floating-point to fixed-point values. The set of vertex coordinates is decoded from the bitstream. The conversion from floating-point vertex coordinates to fixed-point is performed by multiplying the set of vertex coordinates expressed in floating-point by a predetermined conversion parameter. This predetermined conversion parameter may be, for example, 2 to the power of 8, 2 to the power of 10, or 2 to the power of 16. The mesh may be a complete mesh or a submesh.

[0347] The decoding device 1420 decodes upscale parameters and downscale parameters from the bitstream (S1502). The upscale parameters are parameters related to the enlargement process, and the downscale parameters are parameters related to the reduction process. The upscale parameters and downscale parameters may be decoded from the header of the bitstream. The header may be SEI (Supplemental Enhancement Information). The upscale parameters and downscale parameters may be integer values ​​or powers of two.

[0348] The decoding device 1420 derives a set of two-dimensional coordinates based on the set of vertex coordinates (S1503). This set of two-dimensional coordinates is a set obtained by projecting the set of vertex coordinates onto a two-dimensional plane. The set of vertex coordinates may be rotated in three-dimensional space (three-dimensionally rotated) before being projected onto the two-dimensional plane. For example, the set of vertex coordinates 1500 shown in FIG. 51 may be rotated 90 degrees counterclockwise about a rotation axis parallel to the z-axis to transform into the set of vertex coordinates 1501 shown in FIG. 52. The parameters (rotation angle) used in this three-dimensional rotation may be decoded from the bitstream. Then, as shown in FIG. 53, the three-dimensionally rotated set of vertex coordinates 1501 may be projected onto the x-z plane to transform into the set of two-dimensional coordinates 1502. The parameters (projection direction) used in the projection may be decoded from the bitstream.

[0349] The decoding device 1420 derives a set of two-dimensional coordinates that have been scaled (enlarged or reduced) using the upscale parameter (S1504). This set of two-dimensional coordinates is a set obtained by multiplying by the upscale parameter. As shown in FIG. 54 , the set of two-dimensional coordinates 1502 may be converted into the set of two-dimensional coordinates 1503 by being enlarged by multiplication with the upscale parameter "2". Note that when the upscale parameter is "1", the set of scaled two-dimensional coordinates is the same as the set of original two-dimensional coordinates. Furthermore, the upscale parameter cannot be "0". Note that the upscale parameter is a parameter that is multiplied by the original value to enlarge the original value, and therefore is a numerical value greater than 1.

[0350] The decoding device 1420 derives a scaled width and height by combining the predetermined width and height with the downscale parameter (S1505). This process includes at least one mathematical operation. For example, the scaled width or height may be the sum of the predetermined width or height and the downscale parameter. For example, the scaled width or height may be the product of the predetermined width or height and a power of two of the downscale parameter. The predetermined width and height may be decoded from the bitstream. The predetermined width or height may be a fixed value.

[0351] The decoding device 1420 derives a set of three-dimensional coordinates using the set of scaled two-dimensional coordinates (S1506). In this process, the decoding device 1420 normalizes the set of two-dimensional coordinates by the scaled width and height, and introduces a third-axis coordinate value with a value of 1 into the normalized two-dimensional coordinates. That is, the decoding device 1420 adds the third-axis coordinate value to the two-dimensional coordinates to calculate coordinates expanded to three dimensions. This normalization may be performed by division or right bit shift. The normalized two-dimensional coordinates are converted into coordinates represented by floating point, and a third-axis coordinate value with a value of 1 is added before deriving the three-dimensional coordinates. This conversion to coordinates represented by floating point is performed by dividing the normalized two-dimensional coordinates by a predetermined conversion parameter.

[0352] The decoding device 1420 reconstructs a 3D mesh using the set of 3D coordinates (S1507), which is used to map a texture onto the vertices of the 3D mesh.

[0353] 55 is a flowchart showing an example of the scaling process in step S1505 and the normalization process in S1506. Here, the predetermined width and height may be indexes of powers of 2. Also, the downscale parameter and the upscale parameter may be indexes of powers of 2.

[0354] The decoding device 1420 adds the downscale parameter to the predetermined width and predetermined height to calculate the scaled width and height, respectively (S1511).

[0355] The decoding device 1420 bit-shifts the x-axis coordinate and the y-axis coordinate of the set of scaled two-dimensional coordinates to the right to derive a set of three-dimensional coordinates (S1512). Specifically, the decoding device 1420 bit-shifts the x-axis of the set of scaled two-dimensional coordinates to the right by the scaled width to derive the x-axis coordinate of the set of three-dimensional coordinates. In this case, the decoding device 1420 adds an offset (1<<(scaled width-1)) before the bit-shift. Similarly, the decoding device 1420 bit-shifts the y-axis of the set of scaled two-dimensional coordinates to the right by the scaled height to derive the y-axis coordinate of the set of three-dimensional coordinates. In this case, the decoding device 1420 adds an offset (1<<(scaled height-1)) before the bit-shift. The decoding device 1420 sets the z-axis coordinates of all three-dimensional coordinates in the set of three-dimensional coordinates to "1".

[0356] FIG. 56 is a flowchart showing another example of the scaling process in step S1505 and the normalization process in S1506.

[0357] The decoding device 1420 multiplies the predetermined width and predetermined height by the downscale parameter to calculate the scaled width and height, respectively (S1521). Note that the downscale parameter is a parameter used in the reduction process, and is a parameter used to reduce the original value by being multiplied with the original value, so it is a numerical value smaller than 1. Therefore, the downscale parameter may be expressed as a fraction smaller than 1.

[0358] The decoding device 1420 derives a set of three-dimensional coordinates from the x-axis coordinate and y-axis coordinate of the set of scaled two-dimensional coordinates (S1522). Specifically, the decoding device 1420 derives the x-axis coordinate of the set of three-dimensional coordinates by dividing the x-axis coordinate of the set of scaled two-dimensional coordinates by the scaled width. Similarly, the decoding device 1420 derives the y-axis coordinate of the set of three-dimensional coordinates by dividing the y-axis coordinate of the set of scaled two-dimensional coordinates by the scaled height. The decoding device 1420 sets the z-axis coordinates of all three-dimensional coordinates in the set of three-dimensional coordinates to "1".

[0359] Here, the enlargement process and the reduction process in the scaling process may be performed together. That is, the scaling process may be performed by combining an upscale parameter and a downscale parameter. The upscale parameter is expressed as a numerical value greater than 1, and the downscale parameter is expressed as a numerical value less than 1. The scaling ratios of the enlargement process and the reduction process included in the scaling process may be expressed as a combination of the upscale parameter and the downscale parameter, and the upscale parameter may represent the numerator of the scaling ratio, and the downscale parameter may represent the denominator of the scaling ratio.

[0360] Fig. 57 is a flowchart showing a variation of step S1505. That is, the decoding device 1420 may execute steps S1531 to S1533 shown in Fig. 57 instead of step S1505. Fig. 58 is a diagram showing an example of two-dimensional rotation.

[0361] By performing steps S1531 to S1533, the decoding device 1420 derives a set of three-dimensional coordinates using the set of scaled two-dimensional coordinates.

[0362] The decoding device 1420 rotates the set of scaled two-dimensional coordinates in two-dimensional space using a rotation angle (two-dimensional rotation) before normalizing the set of scaled two-dimensional coordinates by the scaled width and the scaled height (S1531). As shown in FIG. 58, the set of two-dimensional coordinates 1512 may be obtained by rotating the set of scaled two-dimensional coordinates 1511 right by 90 degrees. This rotation angle is decoded from the bitstream. In other words, the rotation angle may be a value determined by the encoding device 1400. For example, when the rotation angle is 90 degrees, the y-axis of the set of scaled two-dimensional coordinates is inverted, and the x-axis coordinate and the y-axis coordinate are swapped.

[0363] Next, the decoding device 1420 normalizes the set of scaled two-dimensional coordinates using the scaled width and the scaled height to derive a set of three-dimensional coordinates (S1532). This normalization may be performed by division or right bit shifting.

[0364] Furthermore, the decoding device 1420 converts the normalized and scaled two-dimensional coordinates into three-dimensional coordinates by introducing a coordinate value of 1 on the third axis (S1533). Note that the two-dimensional coordinates and the three-dimensional coordinates may be expressed as integer values.

[0365] Fig. 59 is a flowchart showing another variation of step S1505. That is, the decoding device 1420 may execute steps S1541 to S1543 shown in Fig. 59 instead of step S1505. Fig. 60 is a diagram showing an example of shift processing (translation processing) on ​​a set of two-dimensional coordinates.

[0366] The decoding device 1420 derives a set of three-dimensional coordinates using the set of scaled two-dimensional coordinates (S1541). At this time, the set of scaled two-dimensional coordinates is adjusted before being normalized by the scaled width and the scaled height. This adjustment process is a mathematical operation, which includes addition, subtraction, displacement, and shift operations. A set of parameters is used in this process. This set of parameters is decoded from the bitstream.

[0367] Next, the decoding device 1420 normalizes the set of scaled two-dimensional coordinates using the scaled width and the scaled height to derive a set of three-dimensional coordinates (S1542). This normalization may be performed by division or a right bit shift operation.

[0368] Furthermore, the decoding device 1420 converts the normalized two-dimensional coordinates into three-dimensional coordinates by introducing a coordinate value of a third axis whose value is 1 (S1543). Note that the two-dimensional coordinates and the three-dimensional coordinates may be expressed as integer values.

[0369] For example, as shown in Fig. 60, this scaled set of two-dimensional coordinates 1521 is shifted from one position to another within a bounding box 1523. As a result, the set of two-dimensional coordinates 1521 is transformed into a set of two-dimensional coordinates 1522. The amount of shift may be specified by an x-axis offset amount and a y-axis offset amount. The x-axis offset amount and the y-axis offset amount are included in a set of parameters, and may be set to the same value or different values.

[0370] The examples shown in FIGS. 59 and 60 may be implemented by at least partially combining some aspects of S1505.

[0371] As described above, the multiple two-dimensional coordinates may be scaled, rotated, or shifted on a two-dimensional plane. Furthermore, at least two or more of scaling, rotation, and shifting may be performed on the multiple two-dimensional coordinates. That is, at least one of two-dimensional transformations of scaling, rotation, and shifting may be performed on the multiple two-dimensional coordinates, and the multiple two-dimensional coordinates after the two-dimensional transformation are used for texture mapping. That is, the multiple two-dimensional coordinates after the two-dimensional transformation indicate an area in a two-dimensional image that includes a texture, and the multiple two-dimensional coordinates indicate an area that includes a texture that is mapped to a corresponding three-dimensional mesh. The texture is included in the two-dimensional image.

[0372] In this two-dimensional image, an area specified by a plurality of two-dimensional coordinates after the two-dimensional transformation includes a texture that is mapped to a three-dimensional mesh corresponding to the plurality of two-dimensional coordinates. The two-dimensional image may have a plurality of textures that are applied to the plurality of meshes. The plurality of two-dimensional coordinates after the two-dimensional transformation may be set so that the regions of the plurality of textures corresponding to the plurality of meshes do not overlap with each other and so that the region on the two-dimensional image where nothing is set is minimized. In other words, the two-dimensional transformation may be performed with parameters that are set so that the regions of the plurality of textures corresponding to the plurality of meshes do not overlap with each other and so that the region on the two-dimensional image where nothing is set is minimized.

[0373] 61 is a diagram illustrating an example of syntax in the present disclosure, which includes upscale and downscale parameters.

[0374] 62 is a diagram illustrating another example of syntax according to the present disclosure. This example syntax includes various parameters such as a predetermined width, a predetermined height, a parameter for three-dimensional rotation, a projection parameter, a rotation angle, a set of parameters, an upscale parameter, and a downscale parameter. The various parameters may include at least some of the predetermined width, the predetermined height, a parameter for three-dimensional rotation, a projection parameter, a rotation angle, a set of parameters, an upscale parameter, and a downscale parameter, but may not include all of them.

[0375] FIG. 63 is a flowchart showing an example of a coding process for a three-dimensional mesh.

[0376] The encoding device 1400 encodes the set of vertex coordinates into a bitstream (S1551). This set of vertex coordinates is the three-dimensional coordinates of a mesh. The mesh may be a complete mesh or a sub-mesh.

[0377] The encoding device 1400 encodes the upscale parameters and the downscale parameters into a bitstream (S1552). The upscale parameters and the downscale parameters may be encoded into a header of the bitstream. The header may be Supplemental Enhancement Information (SEI). The upscale parameters and the downscale parameters may be integer values.

[0378] The encoding device 1400 derives a set of two-dimensional coordinates based on the set of vertex coordinates (S1553). This set of two-dimensional coordinates is obtained by projecting the set of vertex coordinates onto a two-dimensional plane. The encoding device 1400 may convert the set of two-dimensional coordinates into coordinates represented by fixed-point numbers. The conversion from floating-point vertex coordinates to fixed-point numbers is performed by multiplying the set of floating-point vertex coordinates by a predetermined transformation parameter. This predetermined transformation parameter may be, for example, 2 to the power of 8, 2 to the power of 10, or 2 to the power of 16. The set of vertex coordinates may also be rotated in three-dimensional space (three-dimensional rotation) before being projected onto the two-dimensional plane. This rotation angle in three-dimensional space may be coded into the bitstream. A parameter used for projection (projection direction) may also be coded into the bitstream. Step S1553 corresponds to step S1503.

[0379] The encoding device 1400 derives a set of two-dimensional coordinates that have been scaled (enlarged or reduced) using the upscale parameter (S1554). This set of two-dimensional coordinates is the set obtained by multiplying by the upscale parameter. Step S1554 corresponds to step S1504.

[0380] The encoding device 1400 derives a scaled width and height by combining the predetermined width and height with the downscale parameter (S1555). This process includes at least one mathematical operation. For example, the scaled width or height may be the sum of the predetermined width or height and the downscale parameter. Or, for example, the scaled width or height may be the product of the predetermined width or height and a power of two of the downscale parameter. The predetermined width and height may be coded into the bitstream. The predetermined width or height may be a fixed value. Step S1555 corresponds to step S1505.

[0381] The encoding device 1400 derives a set of three-dimensional coordinates using the set of scaled two-dimensional coordinates (S1556). In this process, the encoding device 1400 normalizes the set of two-dimensional coordinates by the scaled width and height, and introduces a third-axis coordinate value with a value of 1 into the normalized two-dimensional coordinates. That is, the encoding device 1400 calculates coordinates expanded to three dimensions by adding the third-axis coordinate value to the two-dimensional coordinates. This normalization may be performed by division or right bit shift. The normalized two-dimensional coordinates are converted to coordinates represented by floating point, and a third-axis coordinate value with a value of 1 is added before deriving the three-dimensional coordinates. This conversion to coordinates represented by floating point is performed by dividing the normalized two-dimensional coordinates by a predetermined conversion parameter. Step S1556 corresponds to step S1506.

[0382] The plurality of two-dimensional coordinates after the two-dimensional transformation represent an area in the two-dimensional image that includes a texture, and indicate an area onto which the texture of the three-dimensional mesh corresponding to the plurality of two-dimensional coordinates is mapped. The texture is included in the two-dimensional image.

[0383] In this two-dimensional image, an area specified by a plurality of two-dimensional coordinates after the two-dimensional transformation includes an area onto which the texture of a three-dimensional mesh corresponding to the plurality of two-dimensional coordinates is mapped. The two-dimensional image may have a plurality of textures mapped from a plurality of meshes. The plurality of two-dimensional coordinates after the two-dimensional transformation may be set so that the regions of the plurality of textures corresponding to the plurality of meshes do not overlap with each other and so that the region on the two-dimensional image where nothing is set is minimized. In other words, the two-dimensional transformation may be performed with parameters set to satisfy the conditions that the regions of the plurality of textures corresponding to the plurality of meshes do not overlap with each other and so that the region on the two-dimensional image where nothing is set is minimized.

[0384] (Configuration Example) Fig. 64 is a diagram showing an example of the configuration of an encoding device in an embodiment. Fig. 65 is a flowchart showing an example of an encoding method by the encoding device in an embodiment.

[0385] The encoding device 1530 includes a circuit 1531 and a memory 1532 connected to the circuit 1531. The encoding device 1530 is a device that realizes the encoding device 1400.

[0386] The circuit 1531 performs the following operations.

[0387] The circuit 1531 acquires multiple vertices included in a three-dimensional mesh (S1561). The circuit 1531 generates multiple two-dimensional coordinates by projecting the multiple vertices onto a two-dimensional plane (S1562). The circuit 1531 performs two-dimensional transformation on the multiple two-dimensional coordinates based on parameters (S1563). The circuit 1531 generates a bitstream including the parameters (S1564). The multiple two-dimensional coordinates after the two-dimensional transformation are used to map a texture onto the three-dimensional mesh.

[0388] This generates a bitstream containing parameters as information for identifying the area of ​​the two-dimensional image onto which the texture of the three-dimensional mesh is to be mapped, and the decoding device 1540 (see below) that acquires the bitstream can identify the area of ​​the texture to be mapped onto the three-dimensional mesh based on multiple vertices and parameters.

[0389] For example, the two-dimensional transformation may involve scaling a plurality of two-dimensional coordinates, and the parameters may include a scaling factor, such as an upscale parameter or a downscale parameter.

[0390] This allows the decoding device 1540 to know the scaling factors for multiple two-dimensional coordinates, so that the decoding device 1540 can identify the area of ​​the texture to be mapped onto the three-dimensional mesh.

[0391] For example, the two-dimensional transformation includes a process of shifting the positions of multiple two-dimensional coordinates, and the parameters include an offset amount for the shift.

[0392] This allows the decoding device 1540 to know the offset amounts in shifting multiple two-dimensional coordinates, so that the decoding device 1540 can identify the area of ​​the texture to be mapped onto the three-dimensional mesh.

[0393] For example, the two-dimensional transformation includes a process of two-dimensionally rotating a plurality of two-dimensional coordinates, and the parameters include a rotation angle of the two-dimensional rotation.

[0394] This allows the decoding device 1540 to know the rotation angles of the two-dimensional rotation of multiple two-dimensional coordinates, allowing the decoding device 1540 to identify the area of ​​the texture to be mapped onto the three-dimensional mesh.

[0395] For example, in the projection in step S1562, the 3D mesh is rotated three-dimensionally in the 3D space, and the 3D mesh after the 3D rotation is projected onto a 2D plane. The bit stream includes the rotation angle of the 3D rotation.

[0396] This allows the decoding device 1540 to know the rotation angle of the three-dimensional rotation of the three-dimensional mesh, so that the decoding device 1540 can identify the area of ​​the texture to be mapped onto the three-dimensional mesh.

[0397] For example, the scaling ratio includes at least one of an upscale parameter used in the enlargement process and a downscale parameter used in the reduction process.

[0398] For example, the scaling ratio is expressed as a fraction with the upscale parameter as the numerator and the downscale parameter as the denominator.

[0399] For example, at least one of the upscale parameter and the downscale parameter is an integer.

[0400] For example, at least one of the upscale parameter and the downscale parameter is a power of two.

[0401] Fig. 66 is a diagram showing an example of the configuration of a decoding device according to an embodiment. Fig. 67 is a flowchart showing an example of a decoding method performed by the decoding device according to an embodiment.

[0402] The decoding device 1540 includes a circuit 1541 and a memory 1542 connected to the circuit 1541. The decoding device 1540 is a device that realizes the decoding device 1420.

[0403] The circuit 1541 performs the following operations.

[0404] The circuit 1541 acquires a bitstream (S1541). The circuit 1541 acquires multiple vertices included in a three-dimensional mesh and parameters from the bitstream (S1542). The circuit 1541 generates multiple two-dimensional coordinates by projecting the multiple vertices onto a two-dimensional plane (S1543). The circuit 1541 performs two-dimensional transformation on the multiple two-dimensional coordinates based on the parameters (S1544). The multiple two-dimensional coordinates after the two-dimensional transformation are used to map a texture onto the three-dimensional mesh.

[0405] According to this, since the information is obtained from a bitstream that includes parameters as information for identifying the area of ​​the texture to be mapped to the three-dimensional mesh, the decoding device 1540 that has obtained the bitstream can identify the area of ​​the texture to be mapped to the three-dimensional mesh based on multiple vertices and parameters.

[0406] For example, the two-dimensional transformation may involve scaling a plurality of two-dimensional coordinates, and the parameters may include a scaling factor, such as an upscale parameter or a downscale parameter.

[0407] This allows the scaling ratios of multiple two-dimensional coordinates to be obtained, making it possible to identify the area of ​​the texture to be mapped onto the three-dimensional mesh.

[0408] For example, the two-dimensional transformation includes a process of shifting the positions of multiple two-dimensional coordinates, and the parameters include an offset amount for the shift.

[0409] This makes it possible to obtain the offset amounts for shifting a plurality of two-dimensional coordinates, thereby making it possible to identify the area of ​​the texture to be mapped onto the three-dimensional mesh.

[0410] For example, the two-dimensional transformation includes a process of two-dimensionally rotating a plurality of two-dimensional coordinates, and the parameters include a rotation angle of the two-dimensional rotation.

[0411] This makes it possible to obtain the rotation angles of the two-dimensional rotation of a plurality of two-dimensional coordinates, thereby making it possible to identify the area of ​​the texture to be mapped onto the three-dimensional mesh.

[0412] For example, in the projection, a three-dimensional mesh is rotated three-dimensionally in three-dimensional space, and the three-dimensional mesh after the three-dimensional rotation is projected onto a two-dimensional plane. The bit stream includes the rotation angle of the three-dimensional rotation.

[0413] This makes it possible to obtain the rotation angle of the three-dimensional rotation of the three-dimensional mesh, thereby making it possible to identify the area of ​​the texture to be mapped onto the three-dimensional mesh.

[0414] For example, the scaling ratio includes at least one of an upscale parameter used in the enlargement process and a downscale parameter used in the reduction process.

[0415] For example, the scaling ratio is expressed as a fraction with the upscale parameter as the numerator and the downscale parameter as the denominator.

[0416] For example, at least one of the upscale parameter and the downscale parameter is an integer.

[0417] For example, at least one of the upscale parameter and the downscale parameter is a power of two.

[0418] Furthermore, the encoding and decoding devices of the present disclosure may potentially reduce the length of peripheral signaling information and may also reduce the complexity of the decoding process.

[0419] The encoding device and decoding device of the present disclosure may also be implemented by combining at least a part of other aspects. Furthermore, the configuration or processing of the encoding device and decoding device of the present disclosure may be realized by combining a part of the processing shown in any of the flowcharts according to this aspect, a part of the configuration of any of the devices, a part of the syntax, or the like with other aspects.

[0420] Furthermore, the processing performed by the decoding device of the present disclosure may also be performed in the encoding device in the same manner.

[0421] Furthermore, not all of the components described in this embodiment are always necessary, and only some of the components of the encoding device and decoding device of the present disclosure may be included.

[0422] The present disclosure is useful, for example, in encoding devices, decoding devices, transmitting devices, receiving devices, etc. related to three-dimensional meshes, and is applicable to computer graphics systems, three-dimensional data display systems, etc.

[0423] 100 Encoding device 101, 121, 144 Vertex information encoder 102, 145 Connection information encoder 103, 122 Attribute information encoder 104, 204, 1103 Preprocessor 105, 205, 2106 Postprocessor 110 Three-dimensional data encoding system 111, 211 Controller 112, 212 Input / output processor 113 Three-dimensional data encoder 114 System multiplexer 115 Three-dimensional data generator 123 Metadata encoder 124 Multiplexer 131 Vertex image generator 132 Attribute image generator 133 Metadata generator 134 Video encoder 141 Two-dimensional data encoder 142 Mesh data encoder 143 Texture encoder 148 Description encoder 151, 251 Circuit 152, 252 Memory 200 Decoding device 201, 221, 244 Vertex information decoder 202, 245 Connection information decoder 203, 222 Attribute information decoder 210 3D data decoding system 213 3D data decoder 214 System demultiplexer 215, 247 Presentation device 216 User interface 223 Metadata decoder 224 Demultiplexer 231 Vertex information generator 232 Attribute information generator 234 Video decoder 241 2D data decoder 242 Mesh data decoder 243 Texture decoder 246 Mesh reconstructor 248 Description decoder 300 Network 310 External connection device 613 Base mesh decoder 614 Displacement decoder 615 Attribute decoder 616 Other type decoder 617 3D reconstructor 631 Frame header decoder 632 Vertex geometry coordinate predictor 633 Vertex geometry coordinate differential decoder 634 Reconstructor 1231 Demultiplexer 1232 Switch 1233 Static mesh decoder 1234 Mesh buffer 1235 Motion decoder 1236 Base mesh reconstructor 1237 Inverse quantizer 1238, 1243 Video decoder1239 Image unpacker 1240 Inverse quantizer 1241 Inverse wavelet transformer 1242 Reconstructor 1244 Color transformer 1251 Decoded base mesh 1252 Subdivider 1253 Subdivided mesh 1254 Decoded displacement data 1255 Displacer 1256 Decoded 3D mesh 1400 Encoder 1401 Input mesh 1402 Submeshes 1403, 1426 Attribute map 1404 Preprocessor 1405, 1423 Base mesh 1406, 1424 Displacement data 1407, 1425 Metadata 1408 Compressor 1409, 1421, 1431 Bitstream 1411 Base mesh generator 1412 Subdivider 1413 Displacement generator 1420 Decoder 1422 Decompressor 1427 Post-processor 1428 Merged sub-meshes 1429 Output mesh 1432 Decoder 1433 Post-decoding unit 1434 Pre-reconstruction unit 1435 Reconstruction unit 1436 Post-reconstruction unit 1437 Adaptation unit 1438 Final 3D mesh frame 1500, 1501 Set of vertex coordinates 1502, 1503, 1511, 1512, 1521, 1522 Set of 2D coordinates 1523 Bounding box 1530 Encoder 1531, 1541 Circuitry 1532, 1542 Memory 1540 Decoder 4801, 5701, 11001 Decimator 4802, 5702, 11002 Subdivider 4803, 5703, 11003 Displacement vector calculator 4804, 5704, 11004 Wavelet transformer 4805 Inter predictor 4806, 5706, 11006 Quantizer 4807, 5708, 11008 Image packer 4808, 5709, 11009 Video encoder 4811, 5003, 5711, 5805, 11011 Inverse quantizer 4812, 5004, 5006, 5712, 5806, 5808, 11012 Reconstructor4813, 5713, 11013, 5811 Reference buffer 5001, 5801, 11021 Video decoder 5002, 5802, 11022 Image unpacker 5005, 5807 Inverse wavelet transformer 5705, 11005 LoD-based inter predictor 5707, 5804, 11007, 11024 Switch 5710, 11010 Arithmetic encoder 5803, 11023 Arithmetic decoder

Claims

1. Obtain a plurality of vertices included in a three-dimensional mesh, generate a plurality of two-dimensional coordinates by projecting the plurality of vertices onto a two-dimensional plane, perform two-dimensional transformation on the plurality of two-dimensional coordinates based on parameters, generate a bitstream including the parameters, and the plurality of two-dimensional coordinates after the two-dimensional transformation are used for mapping the texture of the three-dimensional mesh. Encoding method.

2. The two-dimensional transformation includes a process of scaling the plurality of two-dimensional coordinates, and the parameter includes a scaling ratio. The encoding method according to claim 1.

3. The two-dimensional transformation includes a process of shifting the positions of the plurality of two-dimensional coordinates, and the parameter includes an offset amount in the shift. The encoding method according to claim 1.

4. The two-dimensional transformation includes a process of two-dimensionally rotating the plurality of two-dimensional coordinates, and the parameter includes a rotation angle of the two-dimensional rotation. The encoding method according to claim 1.

5. In the projection, the three-dimensional mesh is three-dimensionally rotated in three-dimensional space, and the three-dimensional mesh after the three-dimensional rotation is projected onto the two-dimensional plane. The bitstream includes a rotation angle of the three-dimensional rotation. The encoding method according to any one of claims 1 to 4.

6. The scaling ratio includes at least one of an upscale parameter used for enlargement processing and a downscale parameter used for reduction processing. The encoding method according to claim 2.

7. The scaling ratio is represented by a fraction having the upscale parameter as the numerator and the downscale parameter as the denominator. The encoding method according to claim 6.

8. At least one of the upscale parameter and the downscale parameter is an integer. The encoding method according to claim 6 or 7.

9. At least one of the upscale parameter and the downscale parameter is a power of 2. The encoding method according to claim 6 or 7.

10. Obtain a bitstream, obtain a plurality of vertices included in a three-dimensional mesh and parameters from the bitstream, generate a plurality of two-dimensional coordinates by projecting the plurality of vertices onto a two-dimensional plane, perform two-dimensional transformation on the plurality of two-dimensional coordinates based on the parameters, and the plurality of two-dimensional coordinates after the two-dimensional transformation are used for mapping a texture onto the three-dimensional mesh. Decoding method.

11. The two-dimensional transformation includes a process of scaling the plurality of two-dimensional coordinates, and the parameter includes a scaling ratio. The decoding method according to claim 10.

12. The two-dimensional transformation includes a process of shifting the positions of the plurality of two-dimensional coordinates, and the parameter includes an offset amount in the shift. The decoding method according to claim 10.

13. The two-dimensional transformation includes a process of two-dimensionally rotating the plurality of two-dimensional coordinates, and the parameter includes a rotation angle of the two-dimensional rotation. The decoding method according to claim 10.

14. In the projection, the three-dimensional mesh is three-dimensionally rotated in three-dimensional space, and the three-dimensional mesh after the three-dimensional rotation is projected onto the two-dimensional plane. The bitstream includes a rotation angle of the three-dimensional rotation. The decoding method according to any one of claims 10 to 13.

15. The scaling ratio includes at least one of an upscale parameter used for an enlargement process and a downscale parameter used for a reduction process. The decoding method according to claim 11.

16. The scaling ratio is represented as a fraction having the upscale parameter as the numerator and the downscale parameter as the denominator. The decoding method according to claim 15.

17. At least one of the upscale parameter and the downscale parameter is an integer. The decoding method according to claim 15 or 16.

18. At least one of the upscale parameter and the downscale parameter is a power of 2. The decoding method according to claim 15 or 16.

19. An encoding device comprising: a circuit and a memory connected to the circuit, wherein in operation, the circuit acquires a plurality of vertices included in a three-dimensional mesh, generates a plurality of two-dimensional coordinates by projecting the plurality of vertices onto a two-dimensional plane, two-dimensionally transforms the plurality of two-dimensional coordinates based on a parameter, generates a bitstream including the parameter, and the plurality of two-dimensional coordinates after the two-dimensional transformation are used for mapping a texture of the three-dimensional mesh.

20. A decoding device comprising: a circuit and a memory connected to the circuit, wherein in operation, the circuit acquires a bitstream, acquires a plurality of vertices included in a three-dimensional mesh and a parameter from the bitstream, generates a plurality of two-dimensional coordinates by projecting the plurality of vertices onto a two-dimensional plane, two-dimensionally transforms the plurality of two-dimensional coordinates based on the parameter, and the plurality of two-dimensional coordinates after the two-dimensional transformation are used for mapping a texture onto the three-dimensional mesh.

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