Point cloud data encoding device, point cloud data encoding method, point cloud data decoding device, and point cloud data decoding method

Abstract

A decoding method according to embodiments may comprise the steps of: decoding geometry data of point cloud data in a bitstream; and decoding attribute data of the point cloud data. An encoding method according to embodiments may comprise the steps of: encoding geometry data of point cloud data; and encoding attribute data of the point cloud data.

Description

Point cloud data encoding device, point cloud data encoding method, point cloud data decoding device, and point cloud data decoding method

[0001] Embodiments relate to a method and apparatus for processing point cloud content.

[0002] Point cloud content is represented as a point cloud, a collection of points within a coordinate system representing three-dimensional space. Point cloud content can represent three-dimensional media and is used to provide various services such as VR (Virtual Reality), AR (Augmented Reality), MR (Mixed Reality), and autonomous driving services. However, representing point cloud content requires tens to hundreds of thousands of point data. Therefore, a method for efficiently processing massive amounts of point data is required.

[0003] Embodiments provide devices and methods for efficiently processing point cloud data. Embodiments provide methods and devices for processing point cloud data to address latency and encoding / decoding complexity.

[0004] However, the scope of the embodiments is not limited to the technical tasks described above, and the scope of the embodiments may be expanded to other technical tasks that can be inferred by a person skilled in the art based on the entire described content.

[0005] A decoding method according to embodiments may include a step of decoding geometry data of point cloud data in a bitstream; and a step of decoding attribute data of the point cloud data. A decoding method according to embodiments may include a step of encoding geometry data of the point cloud data; and a step of encoding attribute data of the point cloud data.

[0006] The device and method according to the embodiments can process point cloud data with high efficiency.

[0007] The device and method according to the embodiments can provide a high quality point cloud service.

[0008] The device and method according to the embodiments can provide point cloud content for providing general services such as VR services and autonomous driving services.

[0009] The drawings are included to further understand the embodiments, and the drawings illustrate the embodiments together with the description related to the embodiments. For a better understanding of the various embodiments described below, reference should be made to the following description of the embodiments in conjunction with the following drawings, in which like reference numerals correspond to corresponding parts throughout the drawings.

[0010] Figure 1 illustrates an example of a point cloud content provision system according to embodiments.

[0011] FIG. 2 is a block diagram illustrating a point cloud content provision operation according to embodiments.

[0012] FIG. 3 illustrates an example of a point cloud encoder according to embodiments.

[0013] Figure 4 shows examples of octree and occupancy codes according to embodiments.

[0014] Figure 5 shows an example of a point configuration by LOD according to embodiments.

[0015] Figure 6 shows an example of a point configuration by LOD according to embodiments.

[0016] Fig. 7 illustrates an example of a point cloud decoder according to embodiments.

[0017] Figure 8 is an example of a transmission device according to embodiments.

[0018] Fig. 9 is an example of a receiving device according to embodiments.

[0019] Fig. 10 shows an example of a structure that can be linked with a point cloud data transmission / reception method / device according to embodiments.

[0020] Figure 11 illustrates sampling of point cloud data according to embodiments.

[0021] Figure 12 illustrates a distance-based LOD sampling omission method according to embodiments.

[0022] Figure 13 illustrates an encoder according to embodiments.

[0023] Figure 14 illustrates encoding of attribute data according to embodiments.

[0024] Fig. 15 shows a decoder according to embodiments.

[0025] Figure 16 illustrates decoding of attribute data according to embodiments.

[0026] Figure 17 illustrates LoD (Level of Detail) generation according to embodiments.

[0027] Figure 18 illustrates subsampling according to embodiments.

[0028] Figure 19 illustrates another order-based periodic subsampling according to embodiments.

[0029] Figure 20 shows a bitstream according to embodiments.

[0030] Figure 21 shows a sequence parameter set (SPS) according to embodiments.

[0031] Figure 22 shows an SPS according to embodiments.

[0032] Figure 23 illustrates an attribute parameter set (APS) according to embodiments.

[0033] Figure 24 shows an APS according to embodiments.

[0034] Figure 25 illustrates a tile parameter set (TPS) according to embodiments.

[0035] Figure 26 shows a TPS according to embodiments.

[0036] Figure 27 illustrates an attribute data header according to embodiments.

[0037] Figure 28 illustrates an attribute data header according to embodiments.

[0038] Figure 29 shows an encoding method according to embodiments.

[0039] Figure 30 shows a decryption method according to embodiments.

[0040] Preferred embodiments of the embodiments are described in detail, examples of which are illustrated in the accompanying drawings. The following detailed description, with reference to the accompanying drawings, is intended to illustrate preferred embodiments of the embodiments, rather than merely show embodiments that can be implemented according to the embodiments. The following detailed description includes details to provide a thorough understanding of the embodiments. However, it will be apparent to those skilled in the art that the embodiments may be practiced without these details.

[0041] While most of the terms used in the examples are commonly used in the field, some terms were arbitrarily selected by the applicant, and their meanings are described in detail in the following descriptions as needed. Therefore, the examples should be understood based on the intended meaning of the terms, not simply their names or meanings.

[0042] Figure 1 illustrates an example of a point cloud content provision system according to embodiments.

[0043] The point cloud content provision system illustrated in FIG. 1 may include a transmission device (10000) and a reception device (10004). The transmission device (10000) and the reception device (10004) are capable of wired and wireless communication to transmit and receive point cloud data.

[0044] A transmission device (10000) according to embodiments can secure, process, and transmit a point cloud video (or point cloud content). According to embodiments, the transmission device (10000) can include a fixed station, a base transceiver system (BTS), a network, an Artificial Intelligence (AI) device and / or system, a robot, an AR / VR / XR device and / or a server, etc. In addition, according to embodiments, the transmission device (10000) can include a device that performs communication with a base station and / or other wireless devices using a wireless access technology (e.g., 5G NR (New RAT), LTE (Long Term Evolution)), a robot, a vehicle, an AR / VR / XR device, a portable device, a home appliance, an IoT (Internet of Things) device, an AI device / server, etc.

[0045] A transmission device (10000) according to embodiments includes a point cloud video acquisition unit (Point Cloud Video Acquisition, 10001), a point cloud video encoder (Point Cloud Video Encoder, 10002), and / or a transmitter (or communication module, 10003).

[0046] A point cloud video acquisition unit (10001) according to embodiments acquires a point cloud video through a processing process such as capture, synthesis, or generation. The point cloud video is point cloud content expressed as a point cloud, which is a collection of points located in a three-dimensional space, and may be referred to as point cloud video data, etc. The point cloud video according to embodiments may include one or more frames. One frame represents a still image / picture. Therefore, the point cloud video may include a point cloud image / frame / picture, and may be referred to as any one of a point cloud image, a frame, and a picture.

[0047] A point cloud video encoder (10002) according to embodiments encodes acquired point cloud video data. The point cloud video encoder (10002) may encode point cloud video data based on point cloud compression coding. The point cloud compression coding according to embodiments may include G-PCC (Geometry-based Point Cloud Compression) coding and / or V-PCC (Video-based Point Cloud Compression) coding or next-generation coding. In addition, the point cloud compression coding according to embodiments is not limited to the above-described embodiment. The point cloud video encoder (10002) may output a bitstream including encoded point cloud video data. The bitstream may include not only encoded point cloud video data but also signaling information related to encoding of the point cloud video data.

[0048] A transmitter (10003) according to embodiments transmits a bitstream including encoded point cloud video data. The bitstream according to embodiments is encapsulated into a file or segment (e.g., streaming segment) and transmitted through various networks such as a broadcast network and / or a broadband network. Although not shown in the drawing, the transmission device (10000) may include an encapsulation unit (or an encapsulation module) that performs an encapsulation operation. In addition, the encapsulation unit may be included in the transmitter (10003) according to embodiments. According to embodiments, the file or segment may be transmitted to a receiving device (10004) through a network or may be stored in a digital storage medium (e.g., USB, SD, CD, DVD, Blu-ray, HDD, SSD, etc.). The transmitter (10003) according to embodiments may communicate with the receiving device (10004) (or receiver (10005)) via a network such as 4G, 5G, or 6G via wired / wireless communication. Additionally, the transmitter (10003) can perform data processing operations required according to a network system (e.g., a communication network system such as 4G, 5G, or 6G). Additionally, the transmission device (10000) can transmit encapsulated data in an on-demand manner.

[0049] A receiving device (10004) according to embodiments includes a receiver (Receiver) 10005, a point cloud video decoder (Point Cloud Decoder) 10006, and / or a renderer (Renderer) 10007. According to embodiments, the receiving device (10004) may include a device, robot, vehicle, AR / VR / XR device, mobile device, home appliance, IoT (Internet of Things) device, AI device / server, etc. that performs communication with a base station and / or other wireless devices using a wireless access technology (e.g., 5G NR (New RAT), LTE (Long Term Evolution)).

[0050] A receiver (10005) according to embodiments receives a bitstream containing point cloud video data or a file / segment in which the bitstream is encapsulated, from a network or a storage medium. The receiver (10005) may perform data processing operations required according to a network system (e.g., a communication network system such as 4G, 5G, or 6G). The receiver (10005) according to embodiments may decapsulate the received file / segment and output a bitstream. In addition, the receiver (10005) according to embodiments may include a decapsulation unit (or decapsulation module) for performing the decapsulation operation. In addition, the decapsulation unit may be implemented as a separate element (or component) from the receiver (10005).

[0051] A point cloud video decoder (10006) decodes a bitstream containing point cloud video data. The point cloud video decoder (10006) can decode the point cloud video data according to how it is encoded (e.g., the reverse process of the operation of the point cloud video encoder (10002)). Accordingly, the point cloud video decoder (10006) can decode the point cloud video data by performing point cloud decompression coding, which is the reverse process of point cloud compression. The point cloud decompression coding includes G-PCC coding.

[0052] The renderer (10007) renders decoded point cloud video data. The renderer (10007) can output point cloud content by rendering not only point cloud video data but also audio data. According to embodiments, the renderer (10007) may include a display for displaying the point cloud content. According to embodiments, the display may not be included in the renderer (10007) but may be implemented as a separate device or component.

[0053] The dotted arrows in the drawing indicate the transmission path of feedback information acquired from the receiving device (10004). The feedback information is information for reflecting the interaction with the user consuming the point cloud content, and includes information about the user (e.g., head orientation information, viewport information, etc.). In particular, when the point cloud content is content for a service requiring interaction with the user (e.g., autonomous driving service, etc.), the feedback information may be transmitted to the content transmitter (e.g., the transmitting device (10000)) and / or the service provider. Depending on the embodiments, the feedback information may be used by the receiving device (10004) as well as the transmitting device (10000), or may not be provided.

[0054] Head orientation information according to embodiments is information about the position, direction, angle, movement, etc. of the user's head. The receiving device (10004) according to embodiments can calculate viewport information based on the head orientation information. The viewport information is information about the area of ​​the point cloud video that the user is looking at. The viewpoint is the point where the user is looking at the point cloud video, and may mean the exact center point of the viewport area. In other words, the viewport is an area centered on the viewpoint, and the size, shape, etc. of the area can be determined by the FOV (Field Of View). Therefore, the receiving device (10004) can extract viewport information based on the vertical or horizontal FOV supported by the device in addition to the head orientation information. In addition, the receiving device (10004) performs gaze analysis, etc. to check the user's point cloud consumption method, the area of ​​the point cloud video that the user is looking at, the gaze time, etc. According to embodiments, the receiving device (10004) may transmit feedback information including gaze analysis results to the transmitting device (10000). The feedback information according to embodiments may be acquired during a rendering and / or display process. The feedback information according to embodiments may be acquired by one or more sensors included in the receiving device (10004). Additionally, according to embodiments, the feedback information may be acquired by a renderer (10007) or a separate external element (or device, component, etc.). The dotted line in Fig. 1 represents a transmission process of feedback information acquired by the renderer (10007). The point cloud content providing system may process (encode / decode) point cloud data based on the feedback information. Therefore, the point cloud video data decoder (10006) may perform a decoding operation based on the feedback information.Additionally, the receiving device (10004) can transmit feedback information to the transmitting device (10000). The transmitting device (10000) (or point cloud video data encoder (10002)) can perform an encoding operation based on the feedback information. Therefore, the point cloud content providing system can efficiently process necessary data (e.g., point cloud data corresponding to the user's head position) based on the feedback information without processing (encoding / decoding) all point cloud data, and provide point cloud content to the user.

[0055] According to embodiments, the transmitting device (10000) may be referred to as an encoder, a transmitting device, a transmitter, etc., and the receiving device (10004) may be referred to as a decoder, a receiving device, a receiver, etc.

[0056] Point cloud data processed (processed through a series of processes of acquisition / encoding / transmission / decoding / rendering) in the point cloud content providing system of FIG. 1 according to embodiments may be referred to as point cloud content data or point cloud video data. According to embodiments, point cloud content data may be used as a concept including metadata or signaling information related to point cloud data.

[0057] The elements of the point cloud content provision system illustrated in FIG. 1 may be implemented by hardware, software, a processor, and / or a combination thereof.

[0058] FIG. 2 is a block diagram illustrating a point cloud content provision operation according to embodiments.

[0059] The block diagram of Fig. 2 illustrates the operation of the point cloud content provision system described in Fig. 1. As described above, the point cloud content provision system can process point cloud data based on point cloud compression coding (e.g., G-PCC).

[0060] A point cloud content providing system according to embodiments (e.g., a point cloud transmission device (10000) or a point cloud video acquisition unit (10001)) can acquire a point cloud video (20000). The point cloud video is expressed as a point cloud belonging to a coordinate system representing a three-dimensional space. The point cloud video according to embodiments can include a Ply (Polygon File format or the Stanford Triangle format) file. If the point cloud video has one or more frames, the acquired point cloud video can include one or more Ply files. The Ply file includes point cloud data such as the geometry and / or attributes of points. The geometry includes the positions of points. The position of each point can be expressed as parameters (e.g., values ​​of each of the X-axis, Y-axis, and Z-axis) representing a three-dimensional coordinate system (e.g., a coordinate system composed of XYZ axes). Attributes include attributes of points (e.g., texture information of each point, color (YCbCr or RGB), reflectance (r), transparency, etc.). A point has one or more attributes (or properties). For example, a point may have one attribute, color, or two attributes, color and reflectance. According to embodiments, geometry may be referred to as positions, geometry information, geometry data, etc., and attributes may be referred to as attributes, attribute information, attribute data, etc.Additionally, a point cloud content provision system (e.g., a point cloud transmission device (10000) or a point cloud video acquisition unit (10001)) can obtain point cloud data from information related to the acquisition process of a point cloud video (e.g., depth information, color information, etc.).

[0061] A point cloud content providing system according to embodiments (e.g., a transmission device (10000) or a point cloud video encoder (10002)) can encode point cloud data (20001). The point cloud content providing system can encode point cloud data based on point cloud compression coding. As described above, point cloud data can include geometry and attributes of points. Therefore, the point cloud content providing system can perform geometry encoding to encode geometry and output a geometry bitstream. The point cloud content providing system can perform attribute encoding to encode attributes and output an attribute bitstream. According to embodiments, the point cloud content providing system can perform attribute encoding based on geometry encoding. The geometry bitstream and the attribute bitstream according to embodiments can be multiplexed and output as a single bitstream. A bitstream according to embodiments may further include signaling information related to geometry encoding and attribute encoding.

[0062] A point cloud content providing system according to embodiments (e.g., a transmission device (10000) or a transmitter (10003)) can transmit encoded point cloud data (20002). As described in FIG. 1, the encoded point cloud data can be expressed as a geometry bitstream and an attribute bitstream. In addition, the encoded point cloud data can be transmitted in the form of a bitstream together with signaling information related to encoding of the point cloud data (e.g., signaling information related to geometry encoding and attribute encoding). In addition, the point cloud content providing system can encapsulate a bitstream that transmits the encoded point cloud data and transmit it in the form of a file or segment.

[0063] A point cloud content providing system according to embodiments (e.g., a receiving device (10004) or a receiver (10005)) can receive a bitstream including encoded point cloud data. In addition, the point cloud content providing system (e.g., a receiving device (10004) or a receiver (10005)) can demultiplex the bitstream.

[0064] A point cloud content providing system (e.g., a receiving device (10004) or a point cloud video decoder (10005)) can decode encoded point cloud data (e.g., a geometry bitstream, an attribute bitstream) transmitted as a bitstream. The point cloud content providing system (e.g., a receiving device (10004) or a point cloud video decoder (10005)) can decode the point cloud video data based on signaling information related to encoding of the point cloud video data included in the bitstream. The point cloud content providing system (e.g., a receiving device (10004) or a point cloud video decoder (10005)) can decode the geometry bitstream to restore positions (geometry) of points. The point cloud content providing system can decode the attribute bitstream based on the restored geometry to restore attributes of points. A point cloud content provision system (e.g., a receiving device (10004) or a point cloud video decoder (10005)) can reconstruct a point cloud video based on positions and decoded attributes according to the reconstructed geometry.

[0065] A point cloud content providing system (e.g., a receiving device (10004) or a renderer (10007)) according to embodiments can render decoded point cloud data (20004). The point cloud content providing system (e.g., a receiving device (10004) or a renderer (10007)) can render the decoded geometry and attributes through a decoding process according to various rendering methods. Points of the point cloud content may be rendered as vertices having a certain thickness, cubes having a certain minimum size centered on the vertex position, or circles centered on the vertex position. All or a portion of the rendered point cloud content is provided to a user through a display (e.g., a VR / AR display, a general display, etc.).

[0066] A point cloud content provision system according to embodiments (e.g., a receiving device (10004)) can obtain feedback information (20005). The point cloud content provision system can encode and / or decode point cloud data based on the feedback information. The feedback information and the operation of the point cloud content provision system according to embodiments are identical to the feedback information and operation described in FIG. 1, and therefore, a detailed description thereof will be omitted.

[0067] FIG. 3 illustrates an example of a point cloud encoder according to embodiments.

[0068] FIG. 3 illustrates an example of a point cloud video encoder (10002) of FIG. 1. The point cloud encoder reconstructs point cloud data (e.g., positions and / or attributes of points) and performs an encoding operation to adjust the quality of point cloud content (e.g., lossless, lossy, near-lossless) depending on network conditions or applications. If the total size of the point cloud content is large (e.g., point cloud content of 60 Gbps at 30 fps), the point cloud content provision system may not be able to stream the content in real time. Therefore, the point cloud content provision system can reconstruct the point cloud content based on the maximum target bitrate in order to provide it according to the network environment, etc.

[0069] As described in FIGS. 1 and 2, the point cloud encoder can perform geometry encoding and attribute encoding. Geometry encoding is performed before attribute encoding.

[0070] The point cloud encoder according to the embodiments includes a coordinate system transformation unit (Transformation Coordinates, 30000), a quantization unit (Quantize and Remove Points (Voxelize), 30001), an octree analysis unit (Analyze Octree, 30002), a surface approximation analysis unit (Analyze Surface Approximation, 30003), an arithmetic encoder (Arithmetic Encode, 30004), a geometry reconstruction unit (Reconstruct Geometry, 30005), a color transformation unit (Transform Colors, 30006), an attribute transformation unit (Transfer Attributes, 30007), a RAHT transformation unit (30008), a LOD generation unit (Generated LOD, 30009), a lifting transformation unit (Lifting) (30010), and a coefficient quantization unit (Quantize Coefficients, 30011) and / or an arithmetic encoder (30012).

[0071] The coordinate system transformation unit (30000), the quantization unit (30001), the octree analysis unit (30002), the surface approximation analysis unit (30003), the arithmetic encoder (30004), and the geometry reconstruction unit (30005) can perform geometry encoding. The geometry encoding according to the embodiments can include octree geometry coding, direct coding, trisoup geometry encoding, and entropy encoding. Direct coding and trisoup geometry encoding are applied selectively or in combination. In addition, the geometry encoding is not limited to the above examples.

[0072] As illustrated in the drawing, a coordinate system conversion unit (30000) according to embodiments receives positions and converts them into coordinates. For example, the positions may be converted into location information of a three-dimensional space (e.g., a three-dimensional space expressed in an XYZ coordinate system, etc.). The location information of the three-dimensional space according to embodiments may be referred to as geometry information.

[0073] A quantization unit (30001) according to embodiments quantizes geometry. For example, the quantization unit (30001) may quantize points based on the minimum position value of all points (e.g., the minimum value on each axis for the X-axis, Y-axis, and Z-axis). The quantization unit (30001) performs a quantization operation of multiplying the difference between the minimum position value and the position value of each point by a preset quantization scale value, and then rounding down or up to find the closest integer value. Accordingly, one or more points may have the same quantized position (or position value). The quantization unit (30001) according to embodiments performs voxelization based on the quantized positions to reconstruct the quantized points. The minimum unit containing two-dimensional image / video information is a pixel, and points of point cloud content (or three-dimensional point cloud video) according to embodiments may be included in one or more voxels. A voxel is a combination of a volume and a pixel, and refers to a three-dimensional cubic space generated when a three-dimensional space is divided into units (unit=1.0) based on axes representing the three-dimensional space (e.g., X-axis, Y-axis, Z-axis). The quantization unit (40001) may match groups of points in the three-dimensional space to voxels. According to embodiments, one voxel may include only one point. According to embodiments, one voxel may include one or more points. In addition, in order to express one voxel as one point, the position of the center of the voxel may be set based on the positions of one or more points included in one voxel. In this case, the attributes of all positions contained in one voxel can be combined and assigned to the voxel.

[0074] The octree analysis unit (30002) according to the embodiments performs octree geometry coding (or octree coding) to represent voxels in an octree structure. The octree structure represents points matched to voxels based on an octree structure.

[0075] The surface approximation analysis unit (30003) according to the embodiments can analyze and approximate an octree. The octree analysis and approximation according to the embodiments is a process of analyzing and voxelizing an area including a large number of points to efficiently provide an octree and voxelization.

[0076] An arithmetic encoder (30004) according to embodiments entropy encodes an octree and / or an approximated octree. For example, the encoding method includes an arithmetic encoding method. The encoding results in a geometry bitstream.

[0077] The color conversion unit (30006), the attribute conversion unit (30007), the RAHT conversion unit (30008), the LOD generation unit (30009), the lifting conversion unit (30010), the coefficient quantization unit (30011) and / or the arithmetic encoder (30012) perform attribute encoding. As described above, one point may have one or more attributes. Attribute encoding according to embodiments is applied equally to the attributes of one point. However, when one attribute (e.g., color) includes one or more elements, independent attribute encoding is applied to each element. Attribute encoding according to embodiments may include color transform coding, attribute transform coding, RAHT (Region Adaptive Hierarchial Transform) coding, Interpolarization-based hierarchical nearest-neighbor prediction-Prediction Transform) coding, and lifting transform (interpolation-based hierarchical nearest-neighbor prediction with an update / lifting step (Lifting Transform)) coding. Depending on the point cloud content, the above-described RAHT coding, prediction transform coding, and lifting transform coding may be selectively used, or a combination of one or more codings may be used. In addition, attribute encoding according to embodiments is not limited to the above-described examples.

[0078] The color conversion unit (30006) according to the embodiments performs color conversion coding to convert color values ​​(or textures) included in attributes. For example, the color conversion unit (30006) may convert the format of color information (e.g., convert from RGB to YCbCr). The operation of the color conversion unit (30006) according to the embodiments may be optionally applied depending on the color values ​​included in the attributes.

[0079] The geometry reconstruction unit (30005) according to the embodiments reconstructs (decompresses) an octree and / or an approximated octree. The geometry reconstruction unit (30005) reconstructs an octree / voxel based on the results of analyzing the distribution of points. The reconstructed octree / voxel may be referred to as a reconstructed geometry (or restored geometry).

[0080] The attribute conversion unit (30007) according to the embodiments performs attribute conversion that converts attributes based on positions for which geometry encoding has not been performed and / or reconstructed geometry. As described above, since the attributes are dependent on the geometry, the attribute conversion unit (30007) can convert the attributes based on the reconstructed geometry information. For example, the attribute conversion unit (30007) can convert the attribute of a point at a position based on the position value of the point included in the voxel. As described above, when the position of the center point of a voxel is set based on the positions of one or more points included in the voxel, the attribute conversion unit (30007) converts the attributes of one or more points. When try-soup geometry encoding is performed, the attribute conversion unit (30007) can convert attributes based on the try-soup geometry encoding.

[0081] The attribute transformation unit (30007) can perform attribute transformation by calculating the average value of the attributes or attribute values ​​(e.g., the color or reflectance of each point) of neighboring points within a specific position / radius from the position (or position value) of the center point of each voxel. The attribute transformation unit (30007) can apply a weight according to the distance from the center point to each point when calculating the average value. Accordingly, each voxel has a position and a calculated attribute (or attribute value).

[0082] The attribute transformation unit (30007) can search for neighboring points within a specific position / radius from the position of the center point of each voxel based on the KD tree or the Moulton code. The KD tree is a binary search tree that supports a data structure that can manage points based on their positions to enable fast nearest neighbor search (NNS). The Moulton code represents the coordinate values ​​(e.g. (x, y, z)) indicating the 3D positions of all points as bit values ​​and is generated by mixing the bits. For example, if the coordinate values ​​indicating the position of a point are (5, 9, 1), the bit values ​​of the coordinate values ​​are (0101, 1001, 0001). If the bit values ​​are mixed in the order of z, y, and x according to the bit index, it is 010001000111. If this value is expressed in decimal, it becomes 1095. That is, the Moulton code value of the point with coordinate values ​​(5, 9, 1) is 1095. The attribute transformation unit (30007) can sort points based on the Moulton code value and perform nearest neighbor search (NNS) through a depth-first traversal process. After the attribute transformation operation, if nearest neighbor search (NNS) is also required in other transformation processes for attribute coding, a KD tree or Moulton code is utilized.

[0083] As shown in the drawing, the converted attributes are input to the RAHT conversion unit (30008) and / or the LOD generation unit (30009).

[0084] The RAHT transform unit (30008) according to the embodiments performs RAHT coding to predict attribute information based on reconstructed geometry information. For example, the RAHT transform unit (30008) can predict attribute information of a node at an upper level of an octree based on attribute information associated with a node at a lower level of the octree.

[0085] The LOD generation unit (30009) according to the embodiments generates a LOD (Level of Detail) to perform predictive transformation coding. The LOD according to the embodiments represents the level of detail of point cloud content. A smaller LOD value indicates lower detail of point cloud content, and a larger LOD value indicates higher detail of point cloud content. Points can be classified according to LOD.

[0086] The lifting transformation unit (30010) according to the embodiments performs lifting transformation coding that transforms attributes of a point cloud based on weights. As described above, lifting transformation coding may be applied selectively.

[0087] The coefficient quantization unit (30011) according to the embodiments quantizes attribute-coded attributes based on coefficients.

[0088] An arithmetic encoder (30012) according to embodiments encodes quantized attributes based on arithmetic coding.

[0089] The elements of the point cloud encoder of FIG. 3 may be implemented by hardware, software, firmware, or a combination thereof, including one or more processors or integrated circuits configured to communicate with one or more memories included in the point cloud providing device, although not shown in the drawing. The one or more processors may perform at least one or more of the operations and / or functions of the elements of the point cloud encoder of FIG. 3 described above. Furthermore, the one or more processors may operate or execute a set of software programs and / or instructions for performing the operations and / or functions of the elements of the point cloud encoder of FIG. 3. The one or more memories according to embodiments may include high-speed random access memory, or may include non-volatile memory (e.g., one or more magnetic disk storage devices, flash memory devices, or other non-volatile solid-state memory devices).

[0090] Figure 4 illustrates examples of octree and occupancy codes according to embodiments.

[0091] As described in FIGS. 1 to 3, the point cloud content provision system (point cloud video encoder (10002)) or point cloud encoder (e.g., octree analysis unit (30002)) performs octree geometry coding (or octree coding) based on an octree structure to efficiently manage the area and / or position of a voxel.

[0092] The top of Fig. 4 shows the octree structure. The three-dimensional space of the point cloud content according to the embodiments is expressed by the axes of the coordinate system (e.g., X-axis, Y-axis, Z-axis). The octree structure has two poles (0,0,0) and (2 d , 2 d , 2 d ) is generated by recursively subdividing the cubical axis-aligned bounding box defined by . 2d can be set to a value that constitutes the smallest bounding box that encloses all points of the point cloud content (or point cloud video). d represents the depth of the octree. The value of d is determined by the following equation. In the equation below, (x int n , y int n , z int n ) represents the positions (or position values) of quantized points.

[0093] d=Ceil(Log2(Max(x int n ,y int n ,z int n ,n=1,…,N)+1))

[0094] As shown in the middle of the upper part of Fig. 4, the entire three-dimensional space can be divided into eight spaces according to the division. Each divided space is expressed as a cube with six faces. As shown in the upper right of Fig. 4, each of the eight spaces is again divided based on the axes of the coordinate system (e.g., X-axis, Y-axis, Z-axis). Therefore, each space is again divided into eight smaller spaces. The divided smaller spaces are also expressed as cubes with six faces. This division method is applied until the leaf nodes of the octree become voxels.

[0095] The bottom of Fig. 4 shows the occupancy code of the octree. The occupancy code of the octree is generated to indicate whether each of the eight partitioned spaces generated by partitioning one space contains at least one point. Therefore, one occupancy code is expressed by eight child nodes. Each child node represents the occupancy of the partitioned space, and each child node has a value of 1 bit. Therefore, the occupancy code is expressed as an 8-bit code. That is, if the space corresponding to the child node contains at least one point, the node has a value of 1. If the space corresponding to the child node does not contain a point (empty), the node has a value of 0. Since the occupancy code illustrated in Fig. 4 is 00100001, it indicates that the spaces corresponding to the third and eighth child nodes among the eight child nodes each contain at least one point. As shown in the drawing, the third child node and the eighth child node each have eight child nodes, and each child node is expressed by an 8-bit occupancy code. The drawing shows that the occupancy code of the third child node is 10000111, and the occupancy code of the eighth child node is 01001111. A point cloud encoder according to embodiments (e.g., an arithmetic encoder (30004)) can entropy encode the occupancy code. In addition, the point cloud encoder can intra / inter code the occupancy code to increase compression efficiency. A receiving device according to embodiments (e.g., a receiving device (10004) or a point cloud video decoder (10006)) reconstructs an octree based on the occupancy code.

[0096] A point cloud encoder according to embodiments (e.g., the point cloud encoder of FIG. 3, or the octree analysis unit (30002)) can perform voxelization and octree coding to store the positions of points. However, points within a 3D space are not always evenly distributed, and thus, there may be specific areas where there are not many points. Therefore, performing voxelization on the entire 3D space is inefficient. For example, if there are few points in a specific area, there is no need to perform voxelization up to that area.

[0097] Therefore, the point cloud encoder according to the embodiments can perform direct coding that directly codes the positions of points included in the specific region (or nodes excluding leaf nodes of the octree) without performing voxelization for the specific region described above. The coordinates of the direct coded points according to the embodiments are referred to as a direct coding mode (DCM). In addition, the point cloud encoder according to the embodiments can perform trisoup geometry encoding that reconstructs the positions of points within the specific region (or node) on a voxel basis based on a surface model. Trisoup geometry encoding is a geometry encoding that expresses the representation of an object as a series of triangle meshes. Therefore, the point cloud decoder can generate a point cloud from the mesh surface. Direct coding and trisoup geometry encoding according to the embodiments can be selectively performed. Additionally, direct coding and tri-subtractive geometry encoding according to embodiments may be performed in combination with octree geometry coding (or octree coding).

[0098] In order to perform direct coding, the option to use direct mode for applying direct coding must be activated, the node to which direct coding is to be applied must not be a leaf node, and there must be points below a threshold within a specific node. In addition, the total number of points subject to direct coding must not exceed a preset threshold. If the above conditions are satisfied, the point cloud encoder (or arithmetic encoder (30004)) according to the embodiments can entropy code the positions (or position values) of the points.

[0099] A point cloud encoder according to embodiments (e.g., surface approximation analysis unit (30003)) can determine a specific level of an octree (when the level is smaller than the depth d of the octree) and, starting from that level, perform tri-subject geometry encoding to reconstruct the positions of points within a node region on a voxel basis using a surface model (tri-subject mode). A point cloud encoder according to embodiments can specify a level to which tri-subject geometry encoding is to be applied. For example, when the specified level is equal to the depth of the octree, the point cloud encoder does not operate in tri-subject mode. That is, a point cloud encoder according to embodiments can operate in tri-subject mode only when the specified level is smaller than the depth value of the octree. A three-dimensional cubic area of ​​nodes at a specified level according to embodiments is called a block. One block may include one or more voxels. A block or a voxel may correspond to a brick. Within each block, geometry is represented by a surface. According to embodiments, a surface may intersect each edge of the block at most once.

[0100] Since one block has 12 edges, there are at least 12 intersections within one block. Each intersection is called a vertex. A vertex existing along an edge is detected if there is at least one occupied voxel adjacent to the edge among all blocks sharing the edge. An occupied voxel according to embodiments means a voxel containing a point. The position of a vertex detected along an edge is the average position along the edge of all voxels adjacent to the edge among all blocks sharing the edge.

[0101] When a vertex is detected, the point cloud encoder according to the embodiments can entropy code the starting point (x, y, z) of the edge, the direction vector (Δx, Δy, Δz) of the edge, and the vertex position value (relative position value within the edge). When the tri-substructure geometry encoding is applied, the point cloud encoder according to the embodiments (e.g., the geometry reconstruction unit (30005)) can perform triangle reconstruction, up-sampling, and voxelization processes to generate restored geometry (reconstructed geometry).

[0102] The vertices located at the edge of a block determine the surface passing through the block. According to the embodiments, the surface is a non-planar polygon. The triangle reconstruction process reconstructs the surface represented by a triangle based on the starting point of the edge, the direction vector of the edge, and the position value of the vertex. The triangle reconstruction process is as follows. ① Calculate the centroid value of each vertex, ② Subtract the centroid value from each vertex value, and ③ Square the values, and then add up all the values ​​to obtain the value.

[0103]

[0104] The minimum of the added values ​​is found, and the projection process is performed according to the axis with the minimum value. For example, if the x element is minimum, each vertex is projected to the x-axis based on the center of the block, and then projected onto the (y, z) plane. If the value output when projected onto the (y, z) plane is (ai, bi), the θ value is found through atan2(bi, ai), and the vertices are sorted based on the θ value. The table below shows the combination of vertices to create a triangle depending on the number of vertices. The vertices are sorted in order from 1 to n. The table below shows that for four vertices, two triangles can be formed depending on the combination of the vertices. The first triangle can be formed by the 1st, 2nd, and 3rd vertices among the sorted vertices, and the second triangle can be formed by the 3rd, 4th, and 1st vertices among the sorted vertices.

[0105] Table 2-1. Triangles formed from vertices ordered 1,… ,n

[0106] n triangles

[0107] 3 (1,2,3)

[0108] 4 (1,2,3), (3,4,1)

[0109] 5 (1,2,3), (3,4,5), (5,1,3)

[0110] 6 (1,2,3), (3,4,5), (5,6,1), (1,3,5)

[0111] 7 (1,2,3), (3,4,5), (5,6,7), (7,1,3), (3,5,7)

[0112] 8 (1,2,3), (3,4,5), (5,6,7), (7,8,1), (1,3,5), (5,7,1)

[0113] 9 (1,2,3), (3,4,5), (5,6,7), (7,8,9), (9,1,3), (3,5,7), (7,9,3)

[0114] 10 (1,2,3), (3,4,5), (5,6,7), (7,8,9), (9,10,1), (1,3,5), (5,7,9), (9,1,5)

[0115] 11 (1,2,3), (3,4,5), (5,6,7), (7,8,9), (9,10,11), (11,1,3), (3,5,7), (7,9,11), (11,3,7)

[0116] 12 (1,2,3), (3,4,5), (5,6,7), (7,8,9), (9,10,11), (11,12,1), (1,3,5), (5,7,9), (9,11,1), (1,5,9)

[0117] The upsampling process is performed to voxelize the triangle by adding points in the middle along the edges. Additional points are generated based on the upsampling factor and the width of the block. The additional points are called refined vertices. A point cloud encoder according to embodiments can voxelize the refined vertices. The point cloud encoder can also perform attribute encoding based on the voxelized positions (or position values).

[0118] Figure 5 shows an example of a point configuration by LOD according to embodiments.

[0119] As described in FIGS. 1 to 4, the encoded geometry is reconstructed (decompressed) before attribute encoding is performed. When direct coding is applied, the geometry reconstruction operation may include changing the arrangement of direct-coded points (e.g., placing the direct-coded points at the front of the point cloud data). When trysoup geometry encoding is applied, the geometry reconstruction process includes triangle reconstruction, upsampling, and voxelization. Since attributes depend on the geometry, attribute encoding is performed based on the reconstructed geometry.

[0120] A point cloud encoder (e.g., LOD generation unit (30009)) can reorganize points by LOD. The drawing shows point cloud content corresponding to LOD. The left side of the drawing shows the original point cloud content. The second figure from the left in the drawing shows the distribution of points of the lowest LOD, and the rightmost figure in the drawing shows the distribution of points of the highest LOD. That is, points of the lowest LOD are sparsely distributed, and points of the highest LOD are densely distributed. That is, as LOD increases in the direction of the arrow indicated at the bottom of the drawing, the interval (or distance) between points becomes shorter.

[0121] Figure 6 shows an example of a point configuration by LOD according to embodiments.

[0122] As described in FIGS. 1 to 5, a point cloud content providing system, or a point cloud encoder (e.g., a point cloud video encoder (10002), the point cloud encoder of FIG. 3, or a LOD generation unit (30009)) can generate a LOD. The LOD is generated by reorganizing points into a set of refinement levels according to a set LOD distance value (or a set of Euclidean distances). The LOD generation process is performed not only in the point cloud encoder but also in the point cloud decoder.

[0123] The upper part of Fig. 6 shows examples of points (P0 to P9) of point cloud content distributed in 3D space. The original order in Fig. 6 represents the order of points P0 to P9 before LOD generation. The LOD-based order in Fig. 6 represents the order of points according to LOD generation. The points are rearranged by LOD. Additionally, a higher LOD includes points belonging to a lower LOD. As shown in Fig. 6, LOD0 includes P0, P5, P4, and P2. LOD1 includes points of LOD0 and P1, P6, and P3. LOD2 includes points of LOD0, points of LOD1, and P9, P8, and P7.

[0124] As described in FIG. 3, the point cloud encoder according to the embodiments can selectively or in combination perform predictive transform coding, lifting transform coding, and RAHT transform coding.

[0125] A point cloud encoder according to embodiments can perform predictive transformation coding to generate a predictor for points and set a predicted attribute (or predicted attribute value) for each point. That is, N predictors can be generated for N points. The predictor according to embodiments can calculate a weight (= 1 / distance) value based on the LOD value of each point, indexing information for neighboring points existing within a distance set for each LOD, and distance values ​​to the neighboring points.

[0126] According to the embodiments, the predicted attribute (or attribute value) is set as the average value of the product of the attributes (or attribute values, for example, color, reflectance, etc.) of neighboring points set in the predictor of each point and the weight (or weight value) calculated based on the distance to each neighboring point. The point cloud encoder according to the embodiments (for example, the coefficient quantization unit (30011)) can quantize and inverse quantize the residual values ​​(which may be referred to as residual attributes, residual attribute values, attribute prediction residual values, etc.) obtained by subtracting the predicted attribute (attribute value) from the attribute (attribute value) of each point. The quantization process is as shown in the following table.

[0127] Attribute prediction residuals quantization pseudo codeint PCCQuantization(int value, int quantStep) {if( value >=0) {return floor(value / quantStep + 1.0 / 3.0);} else {return -floor(-value / quantStep + 1.0 / 3.0);}}

[0128] Attribute prediction residuals inverse quantization pseudo codeint PCCInverseQuantization(int value, int quantStep) {if( quantStep ==0) {return value;} else {return value * quantStep;}}

[0129] A point cloud encoder according to embodiments (e.g., an arithmetic encoder (30012)) can entropy code the quantized and dequantized residuals as described above when there are neighboring points to the predictor of each point. A point cloud encoder according to embodiments (e.g., an arithmetic encoder (30012)) can entropy code the attributes of the point without performing the above-described process when there are no neighboring points to the predictor of each point.

[0130] A point cloud encoder according to embodiments (e.g., lifting transformation unit (30010)) can perform lifting transformation coding by generating a predictor for each point, setting the LOD calculated in the predictor, registering neighboring points, and setting weights according to the distance to the neighboring points. Lifting transformation coding according to embodiments is similar to the above-described predictive transformation coding, but differs in that weights are cumulatively applied to attribute values. The process of cumulatively applying weights to attribute values ​​according to embodiments is as follows.

[0131] 1) Create an array QW (QuantizationWieght) that stores the weight values ​​of each point. The initial value of all elements in QW is 1.0. Add the value obtained by multiplying the weight of the current point's predictor by the QW value of the predictor index of the neighboring node registered in the predictor.

[0132] 2) Lift prediction process: To calculate the predicted attribute value, the weighted value of the point's attribute value is multiplied and subtracted from the existing attribute value.

[0133] 3) Create temporary arrays called updateweight and update and initialize them to 0.

[0134] 4) For each predictor, the calculated weights are multiplied by the weights stored in the QW corresponding to the predictor index, and the resulting weights are cumulatively added to the update weight array as the index of the neighboring node. The update array accumulates the values ​​obtained by multiplying the calculated weights by the attribute values ​​of the indexes of the neighboring nodes.

[0135] 5) Lift update process: For each predictor, the attribute values ​​in the update array are divided by the weight values ​​in the update weight array of the predictor index, and the existing attribute values ​​are added to the divided value.

[0136] 6) For all predictors, the predicted attribute values ​​are calculated by additionally multiplying the updated attribute values ​​through the lift update process by the weights (stored in QW) updated through the lift prediction process. The point cloud encoder according to the embodiments (e.g., coefficient quantization unit (30011)) quantizes the predicted attribute values. In addition, the point cloud encoder (e.g., arithmetic encoder (30012)) entropy-codes the quantized attribute values.

[0137] A point cloud encoder according to embodiments (e.g., a RAHT transform unit (30008)) can perform RAHT transform coding that predicts attributes of upper-level nodes using attributes associated with nodes at lower levels of an octree. RAHT transform coding is an example of attribute intra coding through octree backward scan. A point cloud encoder according to embodiments scans from a voxel to the entire region, and repeats the merging process up to a root node while merging voxels into larger blocks at each step. The merging process according to embodiments is performed only for occupied nodes. The merging process is not performed for empty nodes, and the merging process is performed for the node immediately above the empty node.

[0138] The equation below represents the RAHT transformation matrix. is the level It represents the average attribute value of voxels in . Is and can be calculated from. and The weight of class am.

[0139]

[0140] is a low-pass value, which is used in the merging process at the next higher level. are high-pass coefficients, and the high-pass coefficients at each step are quantized and entropy coded (e.g., encoding of an arithmetic encoder (300012)). The weights are is calculated as . The root node is the last class It is generated as follows:

[0141]

[0142] The gDC values ​​are also quantized and entropy coded, like the high-pass coefficients.

[0143] Fig. 7 illustrates an example of a point cloud decoder according to embodiments.

[0144] The point cloud decoder illustrated in FIG. 7 is an example of a point cloud decoder and can perform a decoding operation, which is the reverse process of the encoding operation of the point cloud encoder described in FIGS. 1 to 6.

[0145] As described in Figure 1, the point cloud decoder can perform geometry decoding and attribute decoding. Geometry decoding is performed before attribute decoding.

[0146] A point cloud decoder according to embodiments includes an arithmetic decoder (7000), an octree synthesizer (7001), a surface approximation synthesizer (7002), a geometry reconstructor (7003), an inverse transform coordinates (7004), an arithmetic decoder (7005), an inverse quantize (7006), a RAHT transform (7007), a LOD generator (7008), an inverse lifting (7009), and / or an inverse transform colors (7010).

[0147] The arithmetic decoder (7000), the octree synthesis unit (7001), the surface oproximation synthesis unit (7002), the geometry reconstruction unit (7003), and the coordinate system inversion unit (7004) can perform geometry decoding. Geometry decoding according to embodiments can include direct coding and trisoup geometry decoding. Direct coding and trisoup geometry decoding are applied selectively. In addition, geometry decoding is not limited to the above examples, and is performed by the reverse process of the geometry encoding described in FIGS. 1 to 6.

[0148] An arithmetic decoder (7000) according to embodiments decodes a received geometry bitstream based on arithmetic coding. The operation of the arithmetic decoder (7000) corresponds to the reverse process of the arithmetic encoder (30004).

[0149] The octree synthesis unit (7001) according to the embodiments can generate an octree by obtaining an occupancy code from a decoded geometry bitstream (or information about the geometry obtained as a result of decoding). A specific description of the occupancy code is as described in FIGS. 1 to 6.

[0150] The surface off-axis synthesis unit (7002) according to the embodiments can synthesize a surface based on the decoded geometry and / or the generated octree when the tri-sub geometry encoding is applied.

[0151] The geometry reconstruction unit (7003) according to the embodiments can regenerate geometry based on the surface and / or decoded geometry. As described in FIGS. 1 to 6, direct coding and try-soup geometry encoding are selectively applied. Therefore, the geometry reconstruction unit (7003) directly retrieves and adds position information of points to which direct coding is applied. In addition, when try-soup geometry encoding is applied, the geometry reconstruction unit (7003) can restore geometry by performing a reconstruction operation of the geometry reconstruction unit (30005), such as triangle reconstruction, up-sampling, and voxelization operations. The specific details are the same as described in FIG. 4 and are therefore omitted. The restored geometry may include a point cloud picture or frame that does not include attributes.

[0152] The coordinate system inverse transformation unit (7004) according to the embodiments can obtain the positions of points by transforming the coordinate system based on the restored geometry.

[0153] The arithmetic decoder (7005), the inverse quantization unit (7006), the RAHT transform unit (7007), the LOD generation unit (7008), the inverse lifting unit (7009), and / or the color inverse transform unit (7010) can perform the attribute decoding described in FIG. 10. The attribute decoding according to embodiments can include RAHT (Region Adaptive Hierarchial Transform) decoding, Interpolaration-based hierarchical nearest-neighbor prediction-Prediction Transform) decoding, and lifting transform (interpolation-based hierarchical nearest-neighbor prediction with an update / lifting step (Lifting Transform)) decoding. The three decodings described above can be used selectively, or a combination of one or more decodings can be used. Additionally, attribute decoding according to embodiments is not limited to the examples described above.

[0154] An arithmetic decoder (7005) according to embodiments decodes an attribute bitstream using arithmetic coding.

[0155] The inverse quantization unit (7006) according to the embodiments inverse quantizes information about the decoded attribute bitstream or the attributes obtained as a result of the decoding and outputs the inverse quantized attributes (or attribute values). The inverse quantization may be selectively applied based on the attribute encoding of the point cloud encoder.

[0156] According to embodiments, the RAHT transform unit (7007), the LOD generator (7008), and / or the inverse lifting unit (7009) may process the reconstructed geometry and the inverse quantized attributes. As described above, the RAHT transform unit (7007), the LOD generator (7008), and / or the inverse lifting unit (7009) may selectively perform a corresponding decoding operation according to the encoding of the point cloud encoder.

[0157] The color inverse transform unit (7010) according to the embodiments performs inverse transform coding to inversely transform the color values ​​(or textures) included in the decoded attributes. The operation of the color inverse transform unit (7010) may be selectively performed based on the operation of the color transform unit (30006) of the point cloud encoder.

[0158] The elements of the point cloud decoder of FIG. 7 may be implemented by hardware, software, firmware, or a combination thereof, including one or more processors or integrated circuits configured to communicate with one or more memories included in a point cloud providing device, although not shown in the drawing. The one or more processors may perform at least one or more of the operations and / or functions of the elements of the point cloud decoder of FIG. 7 described above. Furthermore, the one or more processors may operate or execute a set of software programs and / or instructions for performing the operations and / or functions of the elements of the point cloud decoder of FIG. 7.

[0159] Figure 8 is an example of a transmission device according to embodiments.

[0160] The transmission device illustrated in FIG. 8 is an example of the transmission device (10000) of FIG. 1 (or the point cloud encoder of FIG. 3). The transmission device illustrated in FIG. 8 can perform at least one or more of the same or similar operations and encoding methods as the operations and encoding methods of the point cloud encoder described in FIGS. 1 to 6. A transmission device according to embodiments may include a data input unit (8000), a quantization processing unit (8001), a voxelization processing unit (8002), an octree occupancy code generation unit (8003), a surface model processing unit (8004), an intra / inter coding processing unit (8005), an arithmetic coder (8006), a metadata processing unit (8007), a color conversion processing unit (8008), an attribute conversion processing unit (or a property conversion processing unit) (8009), a prediction / lifting / RAHT conversion processing unit (8010), an arithmetic coder (8011), and / or a transmission processing unit (8012).

[0161] The data input unit (8000) according to the embodiments receives or acquires point cloud data. The data input unit (8000) may perform operations and / or acquisition methods identical or similar to those of the point cloud video acquisition unit (10001) (or the acquisition process (20000) described in FIG. 2).

[0162] The data input unit (8000), quantization processing unit (8001), voxelization processing unit (8002), octree occupancy code generation unit (8003), surface model processing unit (8004), intra / inter coding processing unit (8005), and arithmetic coder (8006) perform geometry encoding. Since the geometry encoding according to the embodiments is the same or similar to the geometry encoding described in FIGS. 1 to 6, a detailed description thereof will be omitted.

[0163] The quantization processing unit (8001) according to the embodiments quantizes geometry (e.g., position values ​​of points or position values). The operation and / or quantization of the quantization processing unit (8001) is identical to or similar to the operation and / or quantization of the quantization unit (30001) described in FIG. 3. The specific description is the same as that described in FIGS. 1 to 6.

[0164] The voxelization processing unit (8002) according to the embodiments voxels the position values ​​of quantized points. The voxelization processing unit (80002) may perform operations and / or processes identical or similar to the operations and / or voxelization processes of the quantization unit (30001) described in FIG. 3. Specific descriptions are identical to those described in FIGS. 1 to 6.

[0165] The octree occupancy code generation unit (8003) according to the embodiments performs octree coding on the positions of voxelized points based on the octree structure. The octree occupancy code generation unit (8003) can generate an occupancy code. The octree occupancy code generation unit (8003) can perform operations and / or methods identical or similar to those of the point cloud encoder (or octree analysis unit (30002)) described in FIGS. 3 and 4. The specific description is the same as that described in FIGS. 1 to 6.

[0166] The surface model processing unit (8004) according to the embodiments can perform tri-subject geometry encoding to reconstruct the positions of points within a specific area (or node) on a voxel basis based on the surface model. The surface model processing unit (8004) can perform operations and / or methods identical or similar to those of the point cloud encoder (e.g., surface approximation analysis unit (30003)) described in FIG. 3. The specific description is the same as that described with reference to FIGS. 1 to 6.

[0167] The intra / inter coding processing unit (8005) according to embodiments can intra / inter code point cloud data. The intra / inter coding processing unit (8005) can perform coding identical to or similar to the intra / inter coding described in FIG. 7. The specific description is identical to that described in FIG. 7. According to embodiments, the intra / inter coding processing unit (8005) can be included in an arithmetic coder (8006).

[0168] An arithmetic coder (8006) according to embodiments entropy encodes an octree and / or an approximated octree of point cloud data. For example, the encoding method includes an arithmetic encoding method. The arithmetic coder (8006) performs operations and / or methods identical or similar to those of the arithmetic encoder (30004).

[0169] The metadata processing unit (8007) according to the embodiments processes metadata regarding point cloud data, such as setting values, and provides the metadata to a necessary processing step, such as geometry encoding and / or attribute encoding. In addition, the metadata processing unit (8007) according to the embodiments may generate and / or process signaling information related to geometry encoding and / or attribute encoding. The signaling information according to the embodiments may be encoded and processed separately from geometry encoding and / or attribute encoding. In addition, the signaling information according to the embodiments may be interleaved.

[0170] The color conversion processing unit (8008), the attribute conversion processing unit (8009), the prediction / lifting / RAHT conversion processing unit (8010), and the arithmetic coder (8011) perform attribute encoding. Since the attribute encoding according to the embodiments is the same as or similar to the attribute encoding described in FIGS. 1 to 6, a detailed description thereof will be omitted.

[0171] The color conversion processing unit (8008) according to the embodiments performs color conversion coding to convert the color values ​​included in the attributes. The color conversion processing unit (8008) can perform color conversion coding based on the reconstructed geometry. The description of the reconstructed geometry is the same as that described with reference to FIGS. 1 to 6. In addition, the color conversion processing unit (8008) performs the same or similar operation and / or method as that of the color conversion unit (30006) described with reference to FIG. 3. A detailed description thereof will be omitted.

[0172] The attribute transformation processing unit (8009) according to embodiments performs attribute transformation to transform attributes based on positions for which geometry encoding has not been performed and / or reconstructed geometry. The attribute transformation processing unit (8009) performs operations and / or methods that are the same as or similar to those of the attribute transformation unit (30007) described in FIG. 3. A detailed description thereof will be omitted. The prediction / lifting / RAHT transformation processing unit (8010) according to embodiments can code transformed attributes by using any one or a combination of RAHT coding, prediction transformation coding, and lifting transformation coding. The prediction / lifting / RAHT transformation processing unit (8010) performs at least one or more of operations that are the same as or similar to those of the RAHT transformation unit (30008), LOD generation unit (30009), and lifting transformation unit (30010) described in FIG. 3. In addition, the description of the prediction transformation coding, lifting transformation coding, and RAHT transformation coding is the same as that described in FIGS. 1 to 6, so a detailed description is omitted.

[0173] An arithmetic coder (8011) according to embodiments can encode coded attributes based on arithmetic coding. The arithmetic coder (8011) performs operations and / or methods identical or similar to those of the arithmetic encoder (300012).

[0174] The transmission processing unit (8012) according to embodiments may transmit each bitstream including encoded geometry and / or encoded attribute, metadata information, or may transmit the encoded geometry and / or encoded attribute, and metadata information as one bitstream. When the encoded geometry and / or encoded attribute, and metadata information according to embodiments are configured as one bitstream, the bitstream may include one or more sub-bitstreams. The bitstream according to embodiments may include signaling information including a Sequence Parameter Set (SPS) for sequence-level signaling, a Geometry Parameter Set (GPS) for signaling geometry information coding, an Attribute Parameter Set (APS) for signaling attribute information coding, and a Tile Parameter Set (TPS) for tile-level signaling, and slice data. The slice data may include information about one or more slices. One slice according to embodiments may include one geometry bitstream (Geom0). 0 ) and one or more attribute bitstreams (Attr0 0 , Attr1 0 ) may be included.

[0175] A slice is a series of syntax elements that represent all or part of a coded point cloud frame.

[0176] A TPS according to embodiments may include information about each tile (e.g., coordinate value information of a bounding box and height / size information, etc.) for one or more tiles. A geometry bitstream may include a header and a payload. The header of a geometry bitstream according to embodiments may include identification information of a parameter set included in GPS (geom_ parameter_set_id), a tile identifier (geom_tile_id), a slice identifier (geom_slice_id), and information about data included in the payload. As described above, a metadata processing unit (8007) according to embodiments may generate and / or process signaling information and transmit it to a transmission processing unit (8012). According to embodiments, elements that perform geometry encoding and elements that perform attribute encoding may share data / information with each other as indicated by a dotted line. The transmission processing unit (8012) according to the embodiments may perform operations and / or transmission methods identical or similar to those of the transmitter (10003). A detailed description thereof is omitted as it is the same as that described in FIGS. 1 and 2.

[0177] Fig. 9 is an example of a receiving device according to embodiments.

[0178] The receiving device illustrated in FIG. 9 is an example of the receiving device (10004) of FIG. 1 (or the point cloud decoder of FIGS. 10 and 11). The receiving device illustrated in FIG. 9 can perform at least one or more of the same or similar operations and decoding methods as the operations and decoding methods of the point cloud decoder described in FIGS. 1 to 11.

[0179] A receiving device according to embodiments may include a receiving unit (9000), a receiving processing unit (9001), an arithmetic decoder (9002), an occupancy code-based octree reconstruction processing unit (9003), a surface model processing unit (triangle reconstruction, up-sampling, voxelization) (9004), an inverse quantization processing unit (9005), a metadata parser (9006), an arithmetic decoder (9007), an inverse quantization processing unit (9008), a prediction / lifting / RAHT inverse transform processing unit (9009), a color inverse transform processing unit (9010), and / or a renderer (9011). Each component of the decoding according to embodiments may perform the reverse process of the component of the encoding according to embodiments.

[0180] The receiving unit (9000) according to the embodiments receives point cloud data. The receiving unit (9000) may perform operations and / or receiving methods identical or similar to those of the receiver (10005) of FIG. 1. A detailed description thereof will be omitted.

[0181] The receiving processing unit (9001) according to the embodiments can obtain a geometry bitstream and / or an attribute bitstream from the received data. The receiving processing unit (9001) can be included in the receiving unit (9000).

[0182] The arithmetic decoder (9002), the occupancy code-based octree reconstruction processing unit (9003), the surface model processing unit (9004), and the inverse quantization processing unit (9005) can perform geometry decoding. Since the geometry decoding according to the embodiments is the same or similar to the geometry decoding described in FIGS. 1 to 10, a detailed description thereof will be omitted.

[0183] An arithmetic decoder (9002) according to embodiments can decode a geometry bitstream based on arithmetic coding. The arithmetic decoder (9002) performs operations and / or coding identical to or similar to those of the arithmetic decoder (7000).

[0184] The occupancy code-based octree reconstruction processing unit (9003) according to embodiments can reconstruct an octree by obtaining an occupancy code from a decoded geometry bitstream (or information about the geometry obtained as a result of decoding). The occupancy code-based octree reconstruction processing unit (9003) performs the same or similar operations and / or methods as those of the octree synthesis unit (7001) and / or the octree generation method. The surface model processing unit (9004) according to embodiments can perform tri-sub geometry decoding and related geometry reconstructing (e.g., triangle reconstruction, up-sampling, voxelization) based on the surface model method when tri-sub geometry encoding is applied. The surface model processing unit (9004) performs the same or similar operations as those of the surface off-ratio synthesis unit (7002) and / or the geometry reconstructing unit (7003).

[0185] The inverse quantization processing unit (9005) according to the embodiments can inverse quantize the decoded geometry.

[0186] The metadata parser (9006) according to the embodiments can parse metadata, such as setting values, contained in the received point cloud data. The metadata parser (9006) can pass the metadata to geometry decoding and / or attribute decoding. A detailed description of the metadata is omitted as it is the same as described in FIG. 8.

[0187] The arithmetic decoder (9007), the inverse quantization processing unit (9008), the prediction / lifting / RAHT inverse transform processing unit (9009), and the color inverse transform processing unit (9010) perform attribute decoding. Since attribute decoding is the same or similar to the attribute decoding described in FIGS. 1 to 10, a detailed description thereof will be omitted.

[0188] An arithmetic decoder (9007) according to embodiments can decode an attribute bitstream using arithmetic coding. The arithmetic decoder (9007) can decode the attribute bitstream based on the reconstructed geometry. The arithmetic decoder (9007) performs operations and / or coding identical or similar to those of the arithmetic decoder (7005).

[0189] The inverse quantization processing unit (9008) according to the embodiments can inverse quantize the decoded attribute bitstream. The inverse quantization processing unit (9008) performs operations and / or methods identical or similar to the operations and / or inverse quantization methods of the inverse quantization unit (7006).

[0190] The prediction / lifting / RAHT inverse transform processing unit (9009) according to embodiments can process reconstructed geometry and inverse quantized attributes. The prediction / lifting / RAHT inverse transform processing unit (9009) performs at least one or more of operations and / or decodings that are identical or similar to the operations and / or decodings of the RAHT transform unit (7007), the LOD generation unit (7008), and / or the inverse lifting unit (7009). The color inverse transform processing unit (9010) according to embodiments performs inverse transform coding for inverse transforming the color value (or texture) included in the decoded attributes. The color inverse transform processing unit (9010) performs operations and / or inverse transform coding that are identical or similar to the operations and / or inverse transform coding of the color inverse transform unit (7010). A renderer (9011) according to embodiments can render point cloud data.

[0191] Fig. 10 shows an example of a structure that can be linked with a point cloud data transmission / reception method / device according to embodiments.

[0192] The structure of FIG. 10 represents a configuration in which at least one of a server (1060), a robot (1010), an autonomous vehicle (1020), an XR device (1030), a smartphone (1040), a home appliance (1050), and / or an HMD (1070) is connected to a cloud network (1010). The robot (1010), the autonomous vehicle (1020), the XR device (1030), the smartphone (1040), or the home appliance (1050) are referred to as devices. In addition, the XR device (1030) may correspond to or be linked with a point cloud data (PCC) device according to embodiments.

[0193] A cloud network (1000) may refer to a network that constitutes part of a cloud computing infrastructure or exists within the cloud computing infrastructure. Here, the cloud network (1000) may be configured using a 3G network, a 4G or LTE (Long Term Evolution) network, or a 5G network.

[0194] The server (1060) is connected to at least one of a robot (1010), an autonomous vehicle (1020), an XR device (1030), a smartphone (1040), a home appliance (1050), and / or an HMD (1070) through a cloud network (1000), and can assist in at least part of the processing of the connected devices (1010 to 1070).

[0195] The HMD (Head-Mount Display) (1070) represents one of the types in which the XR device and / or the PCC device according to the embodiments can be implemented. The HMD type device according to the embodiments includes a communication unit, a control unit, a memory unit, an I / O unit, a sensor unit, and a power supply unit.

[0196] Below, various embodiments of devices (1010 to 1050) to which the above-described technology is applied are described. Here, the devices (1010 to 1050) illustrated in FIG. 10 can be linked / combined with point cloud data transmission / reception devices according to the above-described embodiments.

[0197] <PCC+XR>

[0198] The XR / PCC device (1030) may be implemented as a HMD (Head-Mount Display), a HUD (Head-Up Display) equipped in a vehicle, a television, a mobile phone, a smart phone, a computer, a wearable device, a home appliance, digital signage, a vehicle, a fixed robot, a mobile robot, etc., by applying PCC and / or XR (AR+VR) technology.

[0199] The XR / PCC device (1030) can obtain information about surrounding space or real objects by analyzing 3D point cloud data or image data acquired through various sensors or from external devices to generate location data and attribute data for 3D points, and can render and output an XR object to be output. For example, the XR / PCC device (1030) can output an XR object including additional information about a recognized object in correspondence with the recognized object.

[0200] <PCC+XR+모바일폰>

[0201] The XR / PCC device (1030) can be implemented as a mobile phone (1040) or the like by applying PCC technology.

[0202] The mobile phone (1040) can decode and display point cloud content based on PCC technology.

[0203] <PCC+자율주행+XR>

[0204] Autonomous vehicles (1020) can be implemented as mobile robots, vehicles, unmanned aerial vehicles, etc. by applying PCC technology and XR technology.

[0205] An autonomous vehicle (1020) to which XR / PCC technology is applied may refer to an autonomous vehicle equipped with a means for providing XR images, or an autonomous vehicle that is the subject of control / interaction within an XR image. In particular, an autonomous vehicle (1020) that is the subject of control / interaction within an XR image is distinct from an XR device (1030) and can be linked with each other.

[0206] An autonomous vehicle (1020) equipped with a means for providing XR / PCC images can obtain sensor information from sensors including cameras and output XR / PCC images generated based on the obtained sensor information. For example, the autonomous vehicle (1020) can be equipped with a HUD to output XR / PCC images, thereby providing passengers with XR / PCC objects corresponding to real objects or objects on a screen.

[0207] At this time, when the XR / PCC object is output to the HUD, at least a part of the XR / PCC object may be output so as to overlap with an actual object toward which the passenger's gaze is directed. On the other hand, when the XR / PCC object is output to a display provided inside the autonomous vehicle, at least a part of the XR / PCC object may be output so as to overlap with an object on the screen. For example, the autonomous vehicle (1220) may output XR / PCC objects corresponding to objects such as a lane, another vehicle, a traffic light, a traffic sign, a two-wheeled vehicle, a pedestrian, a building, etc.

[0208] VR (Virtual Reality) technology, AR (Augmented Reality) technology, MR (Mixed Reality) technology and / or PCC (Point Cloud Compression) technology according to the embodiments can be applied to various devices.

[0209] In other words, VR technology is a display technology that provides only CG images of objects or backgrounds in the real world. On the other hand, AR technology refers to a technology that shows a virtually created CG image on top of an image of an actual object. Furthermore, MR technology is similar to the aforementioned AR technology in that it mixes and combines virtual objects in the real world. However, in AR technology, the distinction between real objects and virtual objects created with CG images is clear, and virtual objects are used in a form that complements real objects, whereas in MR technology, virtual objects are considered to have the same characteristics as real objects. A more specific example is the hologram service, which is an application of the aforementioned MR technology.

[0210] However, recently, rather than clearly distinguishing between VR, AR, and MR technologies, they are often referred to as XR (extended reality) technologies. Therefore, embodiments of the present invention are applicable to all VR, AR, MR, and XR technologies. These technologies can be applied to encoding / decoding based on PCC, V-PCC, and G-PCC technologies.

[0211] The PCC method / device according to the embodiments can be applied to a vehicle providing an autonomous driving service.

[0212] Vehicles providing autonomous driving services are connected to PCC devices to enable wired / wireless communication.

[0213] A point cloud data (PCC) transmission and reception device according to embodiments, when connected to a vehicle to enable wired / wireless communication, can receive / process content data related to AR / VR / PCC services that can be provided together with autonomous driving services and transmit the same to the vehicle. In addition, when the point cloud data transmission and reception device is mounted on a vehicle, the point cloud transmission and reception device can receive / process content data related to AR / VR / PCC services and provide the same to a user according to a user input signal input through a user interface device. A vehicle or a user interface device according to embodiments can receive a user input signal. The user input signal according to embodiments can include a signal instructing an autonomous driving service.

[0214] The encoding method and device according to the embodiments may include and perform the transmitting device (10000) of FIG. 1, the point cloud video encoder (10002), the transmitter (10003), the acquisition-encoding-transmission (20000-20001-20002) of FIG. 2, the encoder of FIG. 3, the transmitting device of FIG. 8, the device of FIG. 10, the encoder of FIG. 13 to FIG. 14, the encoder of FIG. 17 to FIG. 19, the bitstream and syntax generation of FIG. 20 to FIG. 27, and the encoding method of FIG. 29.

[0215] The decoding method and device according to the embodiments may include and perform the receiving device (10004), receiver (10005), point cloud video decoder (10006) of FIG. 1, transmission-decoding-rendering (20002-20003-20004) of FIG. 2, decoder of FIG. 7, receiving device of FIG. 9, device of FIG. 10, decoder of FIG. 15 to FIG. 19, bitstream and syntax parsing of FIG. 20 to FIG. 27, and decoding method of FIG. 30.

[0216] The encoding / decoding method according to the embodiments includes a subsampling method for LOD generation.

[0217] The embodiments relate to a method for improving the compression efficiency of attributes of Geometry-based Point Cloud Compression (G-PCC) for compressing 3D point cloud data, and include a sampling method for improving the attribute compression efficiency when generating a level of detail (LOD) during a G-PCC attribute encoding and decoding process.

[0218] For example, the embodiments include a sampling omission method using distance in a periodic sampling method, a signaling method, and a decoding method.

[0219] The embodiments include a method for improving the compression efficiency of Geometry-based Point Cloud Compression (G-PCC) for compressing 3D point cloud data. Hereinafter, the terms encoder, encoder, and decoder may be used interchangeably, respectively.

[0220] A point cloud consists of a collection of points, each of which can have geometry and attribute information. Geometry information includes 3D positional (XYZ) information, while attribute information includes color (RGB, YUV, etc.) and / or reflectance values.

[0221] The G-PCC encoding process can be comprised of dividing a point cloud into tiles by region, dividing each tile into slices for parallel processing, compressing geometry for each slice, and compressing attribute information based on the reconstructed geometry (decoded geometry) based on the positional information changed through compression.

[0222] The G-PCC decoding process can be configured to receive an encoded slice unit geometry bitstream and attribute bitstream, decode the geometry, and decode attribute information based on the geometry reconstructed through the decoding process.

[0223] Octree-based, predictive tree-based, or trisoup-based compression techniques can be used to compress geometry information.

[0224] For attribute information compression, compression techniques based on predicting transform, lifting transform, or RAHT transform can be used.

[0225] Embodiments include a method for obtaining high compression efficiency by generating a Level Of Detail (LOD) more suitable for point cloud content by using the distance between sampled points in generating a Level Of Detail (LOD) of a lifting transformation used for compressing the properties of point cloud content.

[0226] Figure 11 illustrates sampling of point cloud data according to embodiments.

[0227] The encoding method and device according to the embodiments (the transmitting device (10000) of FIG. 1, the point cloud video encoder (10002), the transmitter (10003), the acquisition-encoding-transmission (20000-20001-20002) of FIG. 2, the encoder of FIG. 3, the transmitting device of FIG. 8, the device of FIG. 10, the encoder of FIGS. 13 to 14, the encoder of FIGS. 17 to 19, the bitstream and syntax generation of FIGS. 20 to 27, and the encoding method of FIG. 29) can encode attribute data of point cloud data based on LoD.

[0228] The decoding method and device according to the embodiments (receiving device (10004), receiver (10005), point cloud video decoder (10006) of FIG. 1, transmission-decoding-rendering (20002-20003-20004) of FIG. 2, decoder of FIG. 7, receiving device of FIG. 9, device of FIG. 10, decoder of FIG. 15 to FIG. 19, bitstream and syntax parsing of FIG. 20 to FIG. 27, and decoding method of FIG. 30) can decode attribute data of point cloud data based on LoD.

[0229] The LOD generation method for encoding and decoding can include three methods. For example, the LOD generation method can include 1) a distance-based sampling method, 2) a periodic sampling method, and 3) an octree-based sampling method.

[0230] 1) The distance-based sampling method is a method of classifying LODs based on the distance between points, 2) The periodic sampling method is a method of sorting points by Morton code and periodically classifying every Xth corresponding point into a lower LOD that can be a candidate for the neighbor set, and 3) The octree-based sampling method is a method of constructing an octree for points and selecting points close to the center according to the node level of the octree and classifying them into a lower LOD.

[0231] Among the LOD generation methods based on the Molton order-based sampling method described above, the distance-based method has the highest compression efficiency because the distribution of points before and after sampling is similar, but has the disadvantage of high complexity. In addition, the method using octree nodes also shows high compression performance, but has relatively high complexity because it has to find the point closest to the center position for each node. The periodic sampling method is mainly used in cases where fast encoding and decoding are required, such as LiDAR content. Periodic sampling enables fast LOD generation by performing sampling at high speed, but shows relatively low compression performance because sampling is performed periodically regardless of the characteristics of the content.

[0232] Figure 11 shows the results of sampling for lidar content.

[0233] Figure 11 illustrates an example of the results of sampling actual lidar content. As an example, Figure 11 illustrates an example of a distance-based LOD sampling method.

[0234] As shown in Figure 11, the periodic sampling method results in densely distributed sampled points when points are densely distributed within a specific space. However, due to the nature of LiDAR content, each space has the same reflectance coefficient, resulting in identical predicted values ​​during the lifting transformation prediction process. This can be seen as unnecessary sampling.

[0235] To reiterate, according to one embodiment, FIG. 11 may represent the result of performing periodic sampling on lidar content. Referring to FIG. 11, points of lidar content may be sampled according to a period of 4. In a case where points are appropriately distributed, such as in Area A, one point (1101) may be sampled within a certain area. However, in a case where points are densely concentrated in a specific area, such as Area B, multiple points (1102-1, 1102-2) may be sampled within a certain area. Due to the nature of lidar content, since it has the same reflectance within a certain space, it can all have the same predicted value during the prediction process of the lifting transformation. Therefore, sampling multiple points in a space where points are densely concentrated, such as Area B, may be viewed as unnecessary sampling and may degrade compression performance.

[0236] Therefore, in the embodiments, higher compression performance can be secured in lifting transformation by omitting sampling using the distance from the sampled point in the periodic sampling method.

[0237] Variations and combinations between embodiments are possible. The terms used in this document can be understood based on their intended meaning within the scope widely used in the relevant field.

[0238] The distance-based sampling omission method in periodic LOD subsampling according to the embodiments can be performed and applied in both PCC encoders / decoders.

[0239] 1) LOD generation method based on periodic sampling

[0240] The method according to the embodiments may include a lifting transformation method for attribute encoding / decoding. At this time, LOD may be generated before the lifting transformation in order to perform the lifting transformation. LOD may be generated through a periodic sampling method with a fixed sampling period of low complexity, reflecting the low-latency characteristic of the lidar point cloud. At this time, the sampling-based LOD generation method may sample points belonging to the current point group (LoD level index N) to sample points to be included in the point group (LoD level index N+1). The remaining points that were not sampled may be included in the current point group (LoD level index N).

[0241] At this time, all points may be sorted based on the Molton code order. Therefore, sampling can be performed according to the sampling period value based on the order. For example, if the sampling period is 4, 1 out of 4 points can be sampled. At this time, the last point among the 4 points can be sampled. In addition, periodic sampling can be performed recursively for points included in the lower point group. In other words, sampling can be performed for each level of LOD, and sampling can be performed up to the maximum LOD level.

[0242] 2) Other order-based periodic sampling-based LOD generation methods

[0243] As another embodiment of periodic sampling for LOD generation, periodic sampling can be performed based on a different order than the currently sorted point order. For example, if the current point cloud is sorted by Moulton code, periodic sampling can be performed based on the order before being sorted by Moulton code. In this case, the point order before being sorted by Moulton code can be the same as the order output by the geometry decoder. When this is referred to as the standard order, an index according to the standard point order can be stored separately and used for sampling. Conversely, if the current point cloud is not sorted by Moulton code, an index according to the Moulton code-based order can be stored for each point and used for sampling.

[0244] As another example, the ordering can be re-arranged based on criteria other than the existing sorted order, and periodic sampling can be performed based on the corresponding index. For example, all current points can be ordered based on azimuth, and the indices based on the order can be stored and used for sampling. In this case, if the azimuth is the same, the ordering can be determined based on other values ​​among the geometry values. For example, the radius and the laser index can be the second and third criteria, respectively. Alternatively, the laser index and the radius can be the second and third criteria, respectively.

[0245] In another embodiment, if a criterion other than the existing sorted order is used, the criterion may be changed depending on the laser ID. For example, a specific laser ID group may use an azimuth-based ordering, while another laser ID group may use a radius-based ordering for sampling. Here, a laser ID group may include one or more laser IDs. Alternatively, the ordering criterion may be used adaptively based on the value of one of the three channels of geometry information.

[0246] As another embodiment, the “alt_order_lod_subsampling_type”, which indicates the type of sampling method for LOD generation, can be transmitted from the encoder to the decoder via high-level information. Here, the type can include a Moulton code order, a standard order, an azimuth order, a radial order, a laser order, etc.

[0247] In another embodiment, alternative order-based periodic sampling can be performed when alt_order_lod_subsampling_enabled is 1. alt_order_lod_subsampling_enabled can be transmitted from the encoder to the decoder via high-level information, or can be implicitly determined by the encoder and decoder. “alt_order_lod_subsampling_enabled” can have a value of 0 when attribute loading / decoding is in standard order. It can also have a value of 1 when geometry loading / decoding is performed based on predictive tree.

[0248] 3) Distance-based sampling omission method

[0249] Figure 12 illustrates a distance-based LOD sampling omission method according to embodiments.

[0250] Another embodiment of the periodic LOD sampling method can omit measuring the distance between previously sampled points and points in the current cycle and sampling based on that distance. For example, in cases where many points are densely distributed in a specific spatial area, as shown in FIG. 12, sampling may not be performed because there is a high probability that they will have the same reflection coefficient.

[0251] Here, the reference distance, radius, can be transmitted from the encoder to the decoder. At this time, the radius value can mean the radius. Or, the radius value can mean the square of the radius. In addition, the radius value can be a value input by the user in the encoder. Or, the radius value can be a value calculated by the encoder. The encoder can calculate the representative value of the minimum distance between points and determine it as the radius value. At this time, the representative value can be one of the minimum, maximum, average, median, or mode. Or, it can be a value in a specific quantile order among the entire population after sorting the representative values. For example, it can be determined as a value corresponding to the bottom 85%.

[0252] Additionally, the radius value obtained from the bitstream can vary depending on the LOD index. For example, a right shift operation can be applied by the size of the LOD index. If the received radius value is 3, it can be scaled and used as 6 if the current LOD index is 1, or 12 if the current LOD index is 2.

[0253] Alternatively, different radius values ​​may be transmitted from the encoder to the decoder for each LOD. In this case, the encoder may calculate the distance value to be used for sampling for each LOD index and encode it for each LOD.

[0254] The distance between the current sampling target point and the previously sampled point can be calculated using the sum of the squares of the coordinate values. Alternatively, the sum of the absolute values ​​of the coordinate values ​​can be used. Alternatively, the square of the sum of the absolute values ​​of the coordinate values ​​can be used.

[0255] To explain again, referring to FIG. 12, when the sampling period is 4, if the distance between the sampled point (1201) in the previous period and the sampling target point (1202) of the current period is within the radius value, the sampling target point (1202) of the current period is not sampled and sampling may be omitted. In addition, if the distance between the sampling target point (1203) of the next period and the previously sampled point (1201) exceeds the radius value, the sampling target point (1203) of the next period may be sampled. If the distance between the sampling target point and the previously sampled point is within the radius value, sampling may be omitted, and if it exceeds the radius value, sampling may be performed.

[0256] According to embodiments, the radius representing the distance that serves as a criterion for sampling omission may represent a radius value or a radius square value.

[0257] And according to embodiments, the distance between the sampling target point of the current cycle and the previously sampled point may be the sum of the absolute values ​​of the differences in the coordinate values ​​of each axis, or the square of the sum of the absolute values ​​of the differences in the coordinate values ​​of each axis.

[0258] According to embodiments, the radius value may be included in the bitstream and transmitted from the encoder to the decoder. Additionally, the radius value may be a value input by a user in the encoder. Additionally, the radius value may be a value calculated by the encoder. The encoder may determine a representative value as the radius value using the distance between points. According to embodiments, the representative value may be one of the minimum, maximum, average, median, and mode of the distance between points. Alternatively, the representative value may be set to a value corresponding to a specific quantile (e.g., the bottom 85%) after sorting the distances between all points.

[0259] Depending on the embodiments, the radius value may be set the same for all LOD indices regardless of the LOD index, or may be set differently depending on the LOD index.

[0260] In some embodiments, when the radius value is set differently depending on the LOD index, the encoder may include the radius value set for each LOD index in the bitstream and transmit it to the decoder. Alternatively, the bitstream may include one radius value, and the decoder may set the radius value according to the LOD index according to a predetermined rule. For example, the radius value may be shifted to the left by the size of the LOD index.

[0261] 4) How to obtain sampling cycle

[0262] The sampling period according to the embodiments may be used to sample lower-level points for each LOD level. In this case, different values ​​for the sampling period may be used for each LOD level. The sampling period for each level may be included in High Level Syntax (HLS), such as Sequence Parameter Set (SPS), Geometry Parameter Set (GPS), and Tile Parameter Set (TPS), and transmitted from the encoder to the decoder.

[0263] As another method of obtaining a sampling period, the transmitted level-specific sampling period value may be information expressed as an exponent value of 2. That is, the sampling period may be determined as one of the powers of 2.

[0264] Another way to obtain the sampling period is to use the product of all the period values ​​of the received level-specific sampling period values ​​lower than the current level as the sampling period. For example, if the LOD can be divided into four levels and the values ​​4, 4, 4, 4 are received, the sampling periods for each level can be determined as 4, 16, 64, and 256.

[0265] As another method of obtaining a sampling period, the sum of all period values ​​of levels lower than the current level among the transmitted sampling period values ​​can be used as the sampling period.

[0266] Below we will explain LOD in more detail.

[0267] Describes the general creation process.

[0268] The effect of this process is to represent the LoD structure in the state variables LoD count (LodCnt), LoD point count (LodPtCnt), LoD point index (LodPtIdx), LoD refinement point count (LodRfmtPtCnt), and LoD refinement point index (LodRfmtPtIdx).

[0269] The finest detail level includes all slice geometry. This is identified by detail level index 0.

[0270] Detail levels are iteratively subsampled starting from the finest detail level until either a single point remains or lod_max_levels_minus1 subsampled detail levels are generated. The variable Lvl identifies the detail level to subsample.

[0271] Lvl = 0

[0272] for (; Lvl < lod_max_levels_minus1; Lvl++) {

[0273] if (LodPtCnt[Lvl] == 1)

[0274] break

[0275] … / * subsample LodPtIdx[Lvl] * /

[0276] }

[0277] LodCnt = Lvl + 1

[0278] The coarsest detail level is identified by the detail level index LodCnt - 1. All points at the coarsest detail level are assigned to the refinement list for that coarsest detail level.

[0279] It describes the most minute level of detail.

[0280] The AttrPos point indices at the finest level of detail correspond initially one-to-one with the canonical decoding order of the slice geometry.

[0281] for (ptIdx = 0; ptIdx < PointCnt; ptIdx++)

[0282] LodPtIdx[0][ptIdx] = ptIdx

[0283] LodPtCnt[0] = PointCnt

[0284] Point indices at the finest level of detail are sorted by group in ascending order of their respective Moulton code attribute coordinates. The variable maxPtsPerSort identifies the maximum group size when sorting by group.

[0285] maxPtsPerSort = !attr_canonical_order_enabled && !max_points_per_sort_log2_plus1 ?

[0286] LodPtCnt[0] : 1 << (max_points_per_sort_log2_plus1 - 1)

[0287] The sorted order is the same when decoding all attributes from a single slice with the same attribute coordinate array (AttrPos).

[0288] Note that the requirement for consistent ordering can be met by performing a stable sort on each attribute or by reusing rearranged points. For example, an (inefficient) sorting process might look like this:

[0289] for (benIdx = 0; benIdx < LodPtCnt[0]; benIdx += maxPtsPerSort) {

[0290] endIdx = Min(benIdx + maxPtsPerSort, LodPtCnt[0])

[0291] for (i = benIdx; i < endIdx; i++)

[0292] for (j = i + 1; j < endIdx; j++) {

[0293] iPtIdx = LodPtIdx[0][i]

[0294] jPtIdx = LodPtIdx[0][j]

[0295] iMorton = Morton(AttrPos[iPtIdx][0], AttrPos[iPtIdx][1], AttrPos[iPtIdx][2])

[0296] jMorton = Morton(AttrPos[jPtIdx][0], AttrPos[jPtIdx][1], AttrPos[jPtIdx][2])

[0297] if (iMorton > jMorton)

[0298] Swap(LodPtIdx[0][i], LodPtIdx[0][j])

[0299] }

[0300] }

[0301] Describes the coarsest level of detail.

[0302] After generating the LoD hierarchy, all points at the coarsest detail level are assigned to its refinement list.

[0303] for (i = 0; i < LodPtCnt[LodCnt - 1]; i++)

[0304] LodRfmtPtIdx[LodCnt - 1][i] = LodPtIdx[LodCnt - 1][i]

[0305] Describes the creation of a single level of detail.

[0306] A coarser detail level Lvl + 1 is generated by subsampling the points of detail level Lvl.

[0307] The following definitions are used in the specification of the subsampling process:

[0308] The expression InLodPtCnt is an alias for LodPtCnt[ Lvl ], which is the number of points in the input detail level.

[0309] The expression InLodPtIdx[i] is an alias for the point index of the input detail level, LodPtIdx[ Lvl ][i].

[0310] The expression OutLodPtCnt is an alias for the number of points in the output detail level, LodPtCnt[ Lvl + 1 ].

[0311] The expression OutLodPtIdx[i] is an alias for the point index of the output detail level, LodPtIdx[ Lvl + 1 ][i].

[0312] The expression OutRfmtPtIdx[i] is an alias for LodRfmtPtIdx[ Lvl ][i], the point index in the refinement list for the detail level.

[0313] Subsampling divides points at the input detail level into a refinement list for the output detail level and the input detail level. The division process maintains the relative order of points at the input detail level.

[0314] Subsampling proceeds as follows:

[0315] Block-based subsampling when lod_scalability_enabled is 1 or lod_decimation_mode is 2;

[0316] Periodic subsampling if lod_decimation_mode is 1; or

[0317] Otherwise, distance-based subsampling.

[0318] Explain periodic subsampling.

[0319] If aps_extension_present is 1, geom_tree_type is 1, and attr_canonical_order_enabled is 0, the variable CanonicalLodSubsampling is set to 1. Otherwise, CanonicalLodSubsampling is set to 0.

[0320] Periodic subsampling produces a subsampled output detail level by sampling every single sampling period point at the input detail level.

[0321] When CanonicalLodSubsampling is 0, periodic subsampling produces subsampled output detail levels as follows:

[0322] The sampling period for the current detail level is subsamplingPeriod.

[0323] samplingPeriod := 2 + lod_sampling_period_minus2[Lvl]

[0324] Input points are assigned to output detail levels or refinement lists based on the remainder of the input detail level index divided by the sampling period.

[0325] OutLodPtCnt = outRfmtPtCnt = 0

[0326] for (i = 0; i < InLodPtCnt; i++) {

[0327] if (i % samplingPeriod)

[0328] OutRfmtPtIdx[outRfmtPtCnt++] = InLodPtIdx[i]

[0329] else

[0330] OutLodPtIdx[OutLodPtCnt++] = InLodPtIdx[i]

[0331] }

[0332] If CanonicalLodSubsampling is 1, standard order periodic subsampling produces subsampled output detail levels as follows:

[0333] The sampling period for the current detail level is subsamplingPeriod.

[0334] samplingPeriod := (Lv1==0 1 : canonical_samplingPeriod[Lvl-1]) * (2 +

[0335] lod_sampling_period_minus2[Lvl])

[0336] Input points are assigned to output detail levels or refinement lists based on the remainder of the point index of the input detail level divided by the sampling period.

[0337] OutLodPtCnt = outRfmtPtCnt = 0

[0338] for (i = 0; i < InLodPtCnt; i++) {

[0339] if (InLodPtIdx[i] % samplingPeriod)

[0340] OutRfmtPtIdx[outRfmtPtCnt++] = InLodPtIdx[i]

[0341] else

[0342] OutLodPtIdx[OutLodPtCnt++] = InLodPtIdx[i]

[0343] }

[0344] canonical_samplingPeriod[Lvl] = samplingPeriod

[0345] Describes point decisions for distance-based subsampling.

[0346] The derivation of IsSubsampledPoint indicates whether a point should be assigned to an output detail level.

[0347] A point is assigned to an output detail level unless the square of the distance from a previously assigned point in the set of adjacent blocks within the availability window is less than or equal to the square radius (sqRadius). Each availability window is a 128×128×128 block volume identified by (Bs >> 7, Bt >> 7, Bv >> 7).

[0348] Here is an example of point-by-point decision making. Subsampling creates three levels of detail. By subsampling LoD0 (when Lvl=0), points assigned to LoD1 have a shading radius equal to that of other points in LoD1. is not within. The block size used to subsample LoD0 is BlkSizeLog2 = 1. All points are within a single probability window.

[0349] The encoding device and method according to the embodiments can encode Gaussian splat data, and the decoding device and method can decode Gaussian splat data.

[0350] A Gaussian splat may include a Gaussian splat sequence / frame, and a Gaussian splat may be used interchangeably with a Gaussian splat sequence / frame. A Gaussian splat sequence may include multiple consecutive Gaussian splat frames and may represent a continuous scene, such as a video or motion picture. Each Gaussian splat frame may include Gaussian splats acquired at a specific time, and one frame may correspond to a still scene.

[0351] Each Gaussian splat data can be composed of location information and attribute information.

[0352] First, position information can refer to the center of a Gaussian splat in three-dimensional space, and can represent an absolute or relative position. Furthermore, a Cartesian coordinate system can be used to represent three-dimensional space, or a position in a transformed space can be used depending on the application.

[0353]

[0354] The attribute information can consist of spherical harmonics coefficients, opacity, scale along the axis, rotation, etc.

[0355] The coefficients of the spherical harmonic function are the Laplace transform coefficients for the color of the spherical surface using the spherical harmonic function as a basis to express the color or reflectivity of the Gaussian splat. The coefficients of the spherical harmonic function are divided into one low-frequency component and three bands of high-frequency components to represent the change in color or reflectivity according to the angle of the Gaussian splat and the camera position and angle, and each high-frequency band is expressed by dividing it into 3, 5, or 7 components. By multiplying and fusing 16 coefficients for each band and component of the band of the spherical harmonic function, the change in reflectivity according to the angle of the sphere can be expressed. In the case of color, independent spherical harmonic functions can be configured for the three channels representing the color space.

[0356] Opacity can indicate the transparency of independent Gaussian splats. When multiple Gaussians overlap, transparency can be applied. In an opaque Gaussian splat, distant objects are obscured by their relative distance from the viewpoint, whereas in a transparent Gaussian splat, distant objects are visible through.

[0357] The scale along the three axes (e.g. x, y, z) from the center position for an independent Gaussian splat can be used to represent the volume of the Gaussian splat.

[0358] Rotation can represent a rotation in three-dimensional space around a central location for an independent Gaussian splat. Rotation can be expressed as a quaternion or a Euler angle, and a conversion between the two can be used depending on the application.

[0359] The Gaussian splat data described above can be used in whole or in part. For example, if the low-frequency values ​​of each axis are used for the coefficients of the spherical harmonic function, the color of the Gaussian splat can be expressed based on the representative values ​​of the points within the space occupied by the Gaussian splat. Furthermore, the coefficients of the spherical harmonic function can be configured asymmetrically with respect to the number of high-frequency components for each color axis or for different surface properties, and this can be determined based on the importance or degree of change in the information to be expressed on each color axis.

[0360] Additionally, different coding techniques may be used locally depending on the distribution characteristics of the Gaussian splat. Alternatively, different coding techniques may be used depending on the details to increase compression efficiency.

[0361] Embodiments may include applying different LOD generation methods depending on the distribution characteristics of the Gaussian splat. For example, in an area where the distribution of the Gaussian splat is dense, a distance-based LOD sampling omission method may be applied, and in an area where the distribution of the Gaussian splat is not dense, a sampling method other than the distance-based LOD sampling omission method (e.g., a periodic sampling method, a distance-based sampling method, etc.) may be applied.

[0362] Figure 13 illustrates an encoder according to embodiments.

[0363] Figure 13 is a block diagram of a PCC data encoder. Each component may correspond to hardware, software, a processor, and / or a combination thereof. PCC data may be input to the encoder and encoded to output a geometry information bitstream and an attribute information bitstream. The encoder of Figure 13 may be configured with a memory and / or at least one processor connected to the memory. At least one processor may be configured to perform the operations of each component of Figure 13.

[0364] The data input section can read and set input data (e.g., ply, configuration file, etc.).

[0365] The coordinate system transformation unit can support coordinate system changes, such as changing the xyz axes or converting from the xyz rectangular coordinate system to the spherical coordinate system.

[0366] The geometry information transformation quantization processing unit can adjust the scale by multiplying the x, y, and z values ​​of the geometry location of the point cloud point by the scale (scale = geometry quantization value) setting.

[0367] The spatial partition can be divided into tiles or slices for area-specific access or parallel processing of content.

[0368] The geometry encoding unit can encode spatially divided geometry information to generate a geometry information bitstream.

[0369] The color conversion processor can support attribute type conversion, such as changing RGB color to YUV.

[0370] The color rescaling unit can predict attribute values ​​appropriate for the changed location when the geometry is scaled and the location information values ​​are changed.

[0371] The attribute information encoding unit can receive color-resized original attribute information, restored geometry information, and a reference frame as input and perform encoding to generate an attribute information bitstream.

[0372] The reference frame generation unit can store restored geometry and restored attribute information in a reference frame buffer and transfer reference frame data from the reference frame to other modules.

[0373] Figure 14 illustrates encoding of attribute data according to embodiments.

[0374] Fig. 14 is a block diagram of an attribute data encoding unit included in the encoder of Fig. 13. Each component may correspond to hardware, software, a processor, and / or a combination thereof.

[0375] The LOD generation unit can receive segmented point cloud data and generate LODs, and determine point-by-point neighbors used in lifting transformation and prediction transformation. At this time, the LOD generation unit can be performed when LOD parameters are present.

[0376] The lifting transform unit can generate transform coefficients by performing frequency transformation on attribute information through LOD level-specific prediction and update processes using the generated LOD. The generated transform coefficients can be quantized and transmitted to the attribute information entropy encoding unit. Additionally, an internal inverse transformation can be performed to output restored attribute information.

[0377] Predictive transformation can be performed to predict the current point using neighboring points determined during the LOD generation process. The predicted attribute information and the original attribute information can be converted into differential values ​​called transform coefficients, which can be quantized and passed to the attribute information entropy encoding unit. Furthermore, attribute information can be restored and output through inverse quantization and predictive inverse transformation.

[0378] RAHT can be performed without LOD parameters. It receives segmented point cloud data and performs Region Adaptive Hierarchical Transform (RAHT) to transform it into the frequency domain, generating transform coefficients. These transform coefficients are then quantized and passed to the attribute information entropy encoding unit.

[0379] Fig. 15 shows a decoder according to embodiments.

[0380] The decoder of Fig. 15 can follow the reverse process of the encoder of Fig. 13. Fig. 15 is a block diagram of a PCC data decoder. Each component can correspond to hardware, software, a processor, and / or a combination thereof. The decoder can input encoded geometry information bitstreams and attribute information bitstreams, and output decoded and restored PCC data.

[0381] The geometry information decoding unit can receive a geometry information bitstream and decode it to restore the geometry information.

[0382] The coordinate system inversion unit can restore the changed xyz axes or inversely transform the transformed coordinate system into the xyz orthogonal coordinate system.

[0383] The geometry information conversion dequantization processing unit can restore the signaled scale (scale = geometry quantization value) and apply it to the geometry location x, y, and z values ​​of the restored point.

[0384] Attribute residual information entropy decoding can entropy decode attribute bitstreams.

[0385] The attribute information decryption unit can receive an attribute information bitstream and decrypt it to restore the attribute information.

[0386] The color inversion processing unit can restore the converted attributes to RGB colors.

[0387] The reference frame generation unit can store restored geometry and restored attribute information in a reference frame buffer and transfer reference frame data from the reference frame to other modules.

[0388] Figure 16 illustrates decoding of attribute data according to embodiments.

[0389] Figure 16 is a block diagram of the attribute information decryption unit included in Figure 15. Each component may correspond to hardware, software, a processor, and / or a combination thereof.

[0390] The attribute information entropy decoding unit can receive an attribute information bitstream, decode it, and restore the transform coefficients.

[0391] The LOD generation unit can generate LODs by receiving restored geometry information, and can determine point-by-point neighbors used in lifting transformation and prediction transformation. At this time, the LOD generation unit can be performed when LOD parameters are present.

[0392] The lifting inverse transform can restore attribute information by inversely transforming the input transform coefficients and performing frequency inverse transform through the generated LOD and LOD level-by-LOD level update and prediction process.

[0393] Predictive inverse transformation can restore attributes by combining the current point with the predicted value and the inverse transformation value of the input transformation coefficient using the neighboring points determined during the LOD generation process.

[0394] Inverse RAHT can restore attribute information by performing the reverse process of RAHT by inputting restored geometry information and transformation coefficients.

[0395] Figure 17 illustrates LoD (Level of Detail) generation according to embodiments.

[0396] The encoder and decoder of FIGS. 13 to 16 can further perform a method of generating LOD as in FIG. 17 for attribute encoding and decoding.

[0397] Fig. 17 is a block diagram of the LoD generation unit of Figs. 14 and 16. Each component of Fig. 17 may correspond to hardware, software, a processor, and / or a combination thereof.

[0398] The LOD generation unit can input restored geometry information and output multi-layer LODs.

[0399] The Moulton code calculation unit can calculate the Moulton code by inputting restored geometry information.

[0400] The order storage unit can store indices based on the current point order in the form of a list.

[0401] The Molton code-based sorting unit can sort and output an index list based on the Molton code calculated based on geometry information. At this time, the Molton code-based sorting unit can be performed or omitted depending on a flag indicating whether to use canonical order in the attribute. Additionally, a separate list, a Molton-canonical order mapping list, can be generated that maps indices sorted by Molton code to indices in canonical order.

[0402] The sub-sampling unit can perform sub-sampling on the index list to distinguish the current points by LOD.

[0403] The nearest neighbor search unit can find one or more neighboring points for each point based on geometry and store the index of the point in order to predict and update the lifting transformation for points classified by LOD.

[0404] Figure 18 illustrates subsampling according to embodiments.

[0405] Fig. 18 illustrates a subsampling operation included in the LoD generation method of Fig. 17. Fig. 18 is a block diagram of the subsampling unit of Fig. 17. Each component of Fig. 18 may correspond to hardware, software, a processor, and / or a combination thereof. The subsampling unit may receive an ordered index list as input, perform subsampling, and generate and output an index list according to the LOD.

[0406] The specific method of subsampling is as follows.

[0407] If periodic sampling method is not used, distance-based sampling or octree-based sampling can be performed.

[0408] The distance-based sampling unit can input a list of ordered indices and perform sampling based on the distances between points in the list.

[0409] The octree-based sampling unit receives a list of ordered indices, constructs an octree based on the geometry information of the points in the list, and samples points close to the center of each depth node.

[0410] The sampling period calculation unit can calculate the sampling period using the values ​​transmitted via HLS.

[0411] The standard order-based periodic sub-sampling unit can be performed when the standard order sampling flag is 1. The standard order-based periodic sub-sampling unit can perform sampling based on the order of the restored geometry, or if it is Moulton code-aligned, sampling can be performed based on the Moulton code order.

[0412] If the standard order sampling flag is 0, other point order acquisition parts may be performed.

[0413] Other point order acquisition units can store the index of the order in a list with different criteria than the current point order.

[0414] Other order-based periodic subsampling can perform periodic sampling by inputting a list of indices of different order.

[0415] Figure 19 illustrates another order-based periodic subsampling according to embodiments.

[0416] FIG. 19 is a drawing for more specifically explaining another order-based periodic sub-sampling unit included in FIG. 18.

[0417] Referring to FIG. 19, another order-based periodic sampling unit can input an index list and sample the list through periodic sampling using distance-based sampling omission.

[0418] First, the reference distance can be obtained from the bitstream. Alternatively, the same value can be used by calculating it in the encoder and decoder using the restored geometry values.

[0419] In standard order-based sorting, the input index list can be rearranged into standard order using a Moulton-standard order mapping list.

[0420] Periodic sampling can be performed based on the order of the indexes in the reordered list. Here, points within a certain distance can be omitted from sampling using the previously acquired reference distance. Sampled points are included in the sampling list, and points excluded from sampling can be included in a separate list.

[0421] Finally, the sampling points and the separate points can be reordered again according to Moulton order for subsequent nearest neighbor search steps.

[0422] Figure 20 shows a bitstream according to embodiments.

[0423] The encoding method and device according to the embodiments (the transmitting device (10000) of FIG. 1, the point cloud video encoder (10002), the transmitter (10003), the acquisition-encoding-transmission (20000-20001-20002) of FIG. 2, the encoder of FIG. 3, the transmitting device of FIG. 8, the device of FIG. 10, the encoders of FIGS. 13 to 14 and FIGS. 17 to 19, the bitstream and syntax generation of FIGS. 20 to 27, and the encoding method of FIG. 29) can encode point cloud data and generate parameter information (which may be referred to as signaling information or syntax elements). A bitstream of FIG. 20 including the encoded point cloud data and the parameter information can be generated and transmitted.

[0424] The decoding method and device according to the embodiments (receiving device (10004), receiver (10005), point cloud video decoder (10006) of FIG. 1, transmission-decoding-rendering (20002-20003-20004) of FIG. 2, decoder of FIG. 7, receiving device of FIG. 9, device of FIG. 10, decoder of FIG. 15 to FIG. 19, bitstream and syntax parsing of FIG. 20 to FIG. 27, and decoding method of FIG. 30) can receive the bitstream of FIG. 20 and decode point cloud data based on parameter information.

[0425] In order to add / perform embodiments, related information can be signaled within the bitstream as in Fig. 20. Signaling information according to embodiments can be used at a transmitter (encoder) or a receiver (decoder), etc.

[0426] The encoded point cloud configuration is as follows. A point cloud data encoder that performs geometry encoding and / or attribute encoding processes can generate the encoded point cloud (or bitstream including the point cloud) as follows. In addition, signaling information regarding the point cloud data can be generated and processed by the metadata processing unit of the point cloud data transmission device and included in the point cloud as follows.

[0427] Each abbreviation stands for the following. Each abbreviation may be referred to by other terms within the scope of equivalent meaning: SPS (Sequence Parameter Set), GPS (Geometry Parameter Set), APS (Attribute Parameter Set), TPS (Tile Parameter Set), Geometry (Geom) (Geometry bitstream = geometry slice header + [geometry PU header + Geometry PU data] | geometry slice data), Attribute (Attr) (Attribute bitstream = attribute data unit header + [attribute PU header + attribute PU data] | attribute data unit data)

[0428] Other order-based subsampling related optional information can be added and signaled in SPS, GPS, and TPS.

[0429] Other order-based subsampling related options information can be signaled by adding them to the TPS or the Geometry header / attribute header for each Slice.

[0430] Tiles or slices are provided to allow point clouds to be divided and processed by region.

[0431] When dividing by region, you can set different options for generating neighboring point sets for each region, providing a choice between low complexity and somewhat lower reliability, or conversely, high complexity but high reliability. These settings can vary depending on the receiver's processing capacity.

[0432] Therefore, when a point cloud is divided into tiles, different options can be applied to each tile.

[0433] When a point cloud is divided into slices, different options can be applied to each slice.

[0434] Figure 21 shows a sequence parameter set (SPS) according to embodiments.

[0435] Fig. 21 illustrates the syntax of an SPS within the bitstream of Fig. 20. The method according to the embodiments can signal optional information related to periodic sampling using distance-based sampling omission by adding it to a sequence parameter set (SPS).

[0436] Profile (profile_idc): Indicates that the bitstream conforms to a profile.

[0437] Profile Compatibility Flags (profile_compatibility_flags): If this value is 1, it indicates that the bitstream complies with the profile whose profile_idc is j.

[0438] Number of attribute sets (sps_num_attribute_sets): Indicates the number of coded attributes in the bitstream. The sps_num_attribute_sets value ranges from 0 to 63.

[0439] Attribute dimension (attribute_dimension[ i ]): Indicates the number of components of the i-th attribute.

[0440] Attribute instance ID (attribute_instance_id[ i ]): Represents the instance ID of the i-th attribute.

[0441] Enable alternative order based LoD subsampling (sps_alt_order_lod_subsampling_enabled): Indicates whether to use alternative order based subsampling for all sequences referencing the current SPS.

[0442] Enable distance-based sampling skip (sps_sampling_skip_dist_enabled): Indicates whether to use periodic sampling, which uses periodic distance-based sampling skip, for all sequences referencing the current SPS. If sps_sampling_skip_dist_enabled is 1, it indicates that distance-based periodic sampling skip is used for all sequences referencing the current SPS, and if sps_sampling_skip_dist_enabled is 0, it indicates that distance-based periodic sampling skip is not used for all sequences referencing the current SPS.

[0443] Sampling skip distance (sps_sampling_skip_dist): Indicates the reference distance for sampling skip based on periodic distance in all sequences referencing the current SPS.

[0444] As another embodiment, option information related to periodic sampling using distance-based sampling omission can be signaled by adding it to a Sequence Parameter Set (SPS).

[0445] Figure 22 shows an SPS according to embodiments.

[0446] The method according to the embodiments may further define optional information related to periodic sampling utilizing distance-based sampling omission in the SPS, similar to FIG. 21. For example, referring to FIG. 22, optional information related to distance-based sampling omission may be added to the SPS.

[0447] Profile (profile_idc): Indicates that the bitstream conforms to a profile.

[0448] Profile Compatibility Flags (profile_compatibility_flags): If this value is 1, it indicates that the bitstream complies with the profile whose profile_idc is j.

[0449] Number of attribute sets (sps_num_attribute_sets): Indicates the number of coded attributes in the bitstream. The sps_num_attribute_sets value ranges from 0 to 63.

[0450] Attribute dimension (attribute_dimension[ i ]): Indicates the number of components of the i-th attribute.

[0451] Attribute instance ID (attribute_instance_id[ i ]): Represents the instance ID of the i-th attribute.

[0452] Enable alternative order LoD subsampling (sps_alt_order_lod_subsampling_enabled): Indicates whether to use alternative order-based subsampling for all sequences referencing the current SPS.

[0453] Enable distance-based sampling skip (sps_sampling_skip_dist_enabled): Indicates whether to use periodic sampling, which uses periodic distance-based sampling skip, for all sequences referencing the current SPS. If sps_sampling_skip_dist_enabled is 1, it indicates that distance-based periodic sampling skip is used for all sequences referencing the current SPS, and if sps_sampling_skip_dist_enabled is 0, it indicates that distance-based periodic sampling skip is not used for all sequences referencing the current SPS.

[0454] Sampling skip distance [ lvl ](sps_sampling_skip_dist[ lvl ]): Indicates the reference distance for sampling skip based on the periodic distance for the lvlth LOD level in all sequences referencing the current SPS, by LOD level. If the point of the current sampling period is located within sps_sampling_skip_dist from the point sampled in the previous sampling period, sampling can be skipped in the current sampling period. And if the point of the current sampling period is located outside sps_sampling_skip_dist from the point sampled in the previous sampling period, sampling can be performed in the current sampling period.

[0455] Figure 23 illustrates an attribute parameter set (APS) according to embodiments.

[0456] Figure 23 illustrates the syntax of APS within the Figure 20 bitstream. Optional information related to periodic sampling utilizing distance-based sampling omission according to the attribute information encoding / decoding process can be added to the Attribute Parameter Set.

[0457] Attribute Parameter Set ID (aps_attr_parameter_set_id): Provides an APS identifier that can be referenced by other syntax elements. The aps_attr_parameter_set_id value ranges from 0 to 15 (inclusive).

[0458] Sequence Parameter Set ID (aps_seq_parameter_set_id): Indicates the sps_seq_parameter_set_id value for the active SPS. aps_seq_parameter_set_id values ​​range from 0 to 15 (inclusive).

[0459] Lifting_num_pred_nearest_neighbours: The maximum number of nearest neighbors to use for prediction. The lifting_num_pred_nearest_neighbours value ranges from 1 to xx (inclusive).

[0460] The maximum number of direct predictors (lifting_max_num_direct_predictors) indicates the maximum number of predictors to use for direct prediction. The value of lifting_max_num_direct_predictors ranges from 0 to lifting_num_pred_nearest_neighbours. The value of the MaxNumPredictors variable used in the decoding process is as follows: MaxNumPredictors = lift_max_num_direct_predicots + 1

[0461] Enable Alternative Order LoD Subsampling (aps_alt_order_lod_subsampling_enabled): Indicates whether to use alternative order-based subsampling for all attributes referencing the current APS.

[0462] Enable distance-based sampling skip (aps_sampling_skip_dist_enabled): Indicates whether to use periodic sampling with periodic distance-based sampling skip in all sequences referencing the current APS. If aps_sampling_skip_dist_enabled is 1, it indicates that distance-based periodic sampling skip is used in all sequences referencing the current APS, and if aps_sampling_skip_dist_enabled is 0, it indicates that distance-based periodic sampling skip is not used in all sequences referencing the current APS.

[0463] Sampling skip distance (aps_sampling_skip_dist): Indicates the reference distance for periodic distance-based sampling skipping in all frames referencing the current APS.

[0464] As another example, information regarding periodic sampling options using distance-based sampling omission can be signaled by adding them to the Attribute Parameter Set as follows.

[0465] Figure 24 shows an APS according to embodiments.

[0466] The method according to the embodiments may further define optional information related to periodic sampling utilizing distance-based sampling omission, as illustrated in FIG. 24, in the APS, similar to FIG. 23. For example, referring to FIG. 24, optional information related to distance-based sampling omission may be added to the APS.

[0467] Attribute Parameter Set ID (aps_attr_parameter_set_id): Provides an APS identifier that can be referenced by other syntax elements. The aps_attr_parameter_set_id value ranges from 0 to 15 (inclusive).

[0468] Sequence Parameter Set ID (aps_seq_parameter_set_id): Indicates the sps_seq_parameter_set_id value for the active SPS. aps_seq_parameter_set_id values ​​range from 0 to 15 (inclusive).

[0469] Lifting_num_pred_nearest_neighbours: The maximum number of nearest neighbors to use for prediction. The lifting_num_pred_nearest_neighbours value ranges from 1 to xx (inclusive).

[0470] Lifting_max_num_direct_predictors: This indicates the maximum number of predictors to use for direct prediction. The value of lifting_max_num_direct_predictors ranges from 0 to lifting_num_pred_nearest_neighbours. The value of the MaxNumPredictors variable used in the decoding process is as follows: MaxNumPredictors = lift_max_num_direct_predicots + 1

[0471] Enable Alternative Order LoD Subsampling (aps_alt_order_lod_subsampling_enabled): Indicates whether to use alternative order-based subsampling for all attributes referencing the current APS.

[0472] Enable distance-based sampling skip (aps_sampling_skip_dist_enabled): Indicates whether to use periodic sampling with periodic distance-based sampling skip in all frames referencing the current APS. If aps_sampling_skip_dist_enabled is 1, it indicates that distance-based periodic sampling skip is used in all sequences referencing the current APS, and if aps_sampling_skip_dist_enabled is 0, it indicates that distance-based periodic sampling skip is not used in all sequences referencing the current APS.

[0473] Sampling skip distance [ lvl ] (aps_sampling_skip_dist[ lvl ]): Indicates the reference distance for periodic distance-based sampling skip for the lvlth LOD in all frames referencing the current APS, by LOD index.

[0474] Figure 25 illustrates a tile parameter set (TPS) according to embodiments.

[0475] Figure 25 illustrates the syntax of a TPS within the bitstream of Figure 20. Optional information related to periodic sampling using distance-based sampling omission during the encoding / decoding process can be added to the Tile Parameter Set.

[0476] tile_bounding_box_offset_x[ i ]: The x-offset of the ith tile in Cartesian coordinates. If this value is missing, the value of tile_bounding_box_offset_x

[0000] is inferred to be sps_bounding_box_offset_x.

[0477] The tile bounding box offset y (tile_bounding_box_offset_y[ i ]) represents the y-offset of the ith tile in Cartesian coordinates. If this value is missing, the value of tile_bounding_box_offset_y

[0000] is inferred to be sps_bounding_box_offset_y.

[0478] Tile bounding box offset z (tile_bounding_box_offset_z[ i ]): Indicates the z-offset of the ith tile in Cartesian coordinates. If this value is missing, the value of tile_bounding_box_offset_z

[0000] is inferred to be sps_bounding_box_offset_z.

[0479] Reference Frame Sampling Enabled (reference_frame_sampling_enabled): Indicates whether reference frame sampling is used for the tile.

[0480] Reference sampling threshold (reference_sampling_threshold): Indicates the reference frame sampling threshold applied to the tile (see the description of the other order-based periodic sampling-based LoD generation method described above, 2).

[0481] Reference sampling scale enabled (reference_sampling_scale_enabled): Indicates whether the reference frame sampling attribute coordinate system scale value applied to the tile is applied.

[0482] Enable alternative order LoD subsampling (tile_alt_order_lod_subsampling_enabled[ i ]): Indicates whether to apply alternative order-based subsampling for the i-th tile.

[0483] Enable distance-based sampling skip (tile_sampling_skip_dist_enabled[ i ]): Indicates whether periodic sampling with distance-based sampling skip is used in the i-th tile. If tile_sampling_skip_dist_enabled is 1, it indicates that distance-based periodic sampling skip is used in the i-th tile, and if tile_sampling_skip_dist_enabled is 0, it indicates that distance-based periodic sampling skip is not used in the i-th tile.

[0484] Sampling skip distance (tile_sampling_skip_dist[ i ]): Indicates the reference distance for periodic distance-based sampling skip in the i-th tile.

[0485] Figure 26 shows a TPS according to embodiments.

[0486] The method according to the embodiments can signal periodic sampling-related option information using distance-based sampling omission, as in FIG. 26, by adding it to the Tile Parameter Set, similar to FIG. 25.

[0487] Tile bounding box offset x (tile_bounding_box_offset_x[ i ]): Indicates the x-offset of the ith tile in Cartesian coordinates. If this value is missing, the value of tile_bounding_box_offset_x

[0000] is inferred to be sps_bounding_box_offset_x.

[0488] Tile bounding box offset y (tile_bounding_box_offset_y[ i ]) represents the y-offset of the ith tile in Cartesian coordinates. If this value is missing, the value of tile_bounding_box_offset_y

[0000] is inferred as sps_bounding_box_offset_y.

[0489] Tile bounding box offset z (tile_bounding_box_offset_z[ i ]) represents the z-offset of the ith tile in Cartesian coordinates. If this value is missing, the value of tile_bounding_box_offset_z

[0000] is inferred as sps_bounding_box_offset_z.

[0490] Reference Frame Sampling Enabled (reference_frame_sampling_enabled): Indicates whether reference frame sampling is used for the tile.

[0491] Reference sampling enable (reference_sampling_threshold): Indicates the reference frame sampling threshold applied to the tile (see 2) Other order-based periodic sampling-based LoD generation methods described above).

[0492] Reference sampling scale enabled (reference_sampling_scale_enabled): Indicates whether the reference frame sampling attribute coordinate system scale value applied to the tile is applied.

[0493] Enable tile alternative order LoD subsampling (tile_alt_order_lod_subsampling_enabled[ i ]): Indicates whether to apply alternative order-based subsampling for the i-th tile.

[0494] Enable distance-based sampling skip (tile_sampling_skip_dist_enabled[ i ]): Indicates whether periodic sampling with distance-based sampling skip is used in the i-th tile. If tile_sampling_skip_dist_enabled is 1, it indicates that distance-based periodic sampling skip is used in the i-th tile, and if tile_sampling_skip_dist_enabled is 0, it indicates that distance-based periodic sampling skip is not used in the i-th tile.

[0495] Sampling skip distance (tile_sampling_skip_dist[ i ][ lvl ]_: Indicates the reference distance for periodic distance-based sampling skip for the lvl-th LOD in the i-th tile.

[0496] Figure 27 illustrates an attribute data header according to embodiments.

[0497] Figure 27 illustrates an attribute data header within the bitstream of Figure 20. Optional information related to periodic sampling that utilizes distance-based sampling omission during the encoding / decoding process can be added to the attribute data header.

[0498] Attribute parameter set ID (abh_attr_parameter_set_id): Indicates the abh_attr_parameter_set_id value of the active APS.

[0499] Attribute Sequence Parameter Attribute Index (abh_attr_sps_attr_idx): Indicates the attribute set of the active SPS. The abh_attr_sps_attr_idx value ranges from 0 to sps_num_attribute_sets in the active SPS.

[0500] Attribute Geometry Slice ID (abh_attr_geom_slice_id): Indicates the gsh_slice_id value of the active geometry slice header.

[0501] Enable Alternative Order LoD Subsampling (abh_alt_order_lod_subsampling_enabled): Indicates whether to use alternative order based subsampling for the current slice.

[0502] Enable distance-based sampling skip (abh_sampling_skip_dist_enabled): Indicates whether periodic sampling with periodic distance-based sampling skip is used in the current slice. If abh_sampling_skip_dist_enabled is 1, it indicates that distance-based periodic sampling skip is used in the current slice, and if abh_sampling_skip_dist_enabled is 0, it indicates that distance-based periodic sampling skip is not used in the current slice.

[0503] Sampling skip distance (abh_sampling_skip_dist): Indicates the reference distance for periodic distance-based sampling skipping in the current slice.

[0504] Figure 28 illustrates an attribute data header according to embodiments.

[0505] FIG. 28 illustrates the syntax of option information related to periodic sampling using distance-based sampling omission of the attribute data header in the FIG. 20 bitstream, as in FIG. 27.

[0506] Attribute parameter set ID (abh_attr_parameter_set_id): Indicates the abh_attr_parameter_set_id value of the active APS.

[0507] Attribute Sequence Parameter Set Attribute Index (abh_attr_sps_attr_idx): Indicates the attribute set of the active SPS. The abh_attr_sps_attr_idx value ranges from 0 to sps_num_attribute_sets in the active SPS.

[0508] Attribute Geometry Slice ID (abh_attr_geom_slice_id): Indicates the gsh_slice_id value of the active geometry slice header.

[0509] Enable Alternative Order LoD Subsampling (abh_alt_order_lod_subsampling_enabled): Indicates whether to use alternative order based subsampling for the current slice.

[0510] Enable distance-based sampling skip (abh_sampling_skip_dist_enabled): Indicates whether periodic sampling with periodic distance-based sampling skip is used in the current slice. If abh_sampling_skip_dist_enabled is 1, it indicates that distance-based periodic sampling skip is used in the current slice, and if abh_sampling_skip_dist_enabled is 0, it indicates that distance-based periodic sampling skip is not used in the current slice.

[0511] Sampling skip distance (abh_sampling_skip_dist[ lvl ]): Indicates the reference distance for periodic distance-based sampling skip for the lvlth LOD in the current slice.

[0512] To apply the embodiments, a periodic subsampling method can be added and included in the decoding process and used at the transmitter or receiver.

[0513] Periodic subsampling of the decoder / encoder may involve the following steps:

[0514] Periodic sampling can be performed when CanonicalLodSubsampling is 0. Periodic sampling can be performed sequentially for the input index list. At this time, the sampling period can be included in the bitstream and transmitted from the encoder. The sampling period can have different values ​​for each LOD index. As an example of the periodic sampling method, if the remainder of the current index list order divided by the sampling period is 0, the index corresponding to the order can be sampled and added to the upper LOD index list, Out Refinement Point Index (OutRfmtPtIdx). In addition, indices with a non-zero remainder can be added to the Out LoD Point Index (OutLodPtIdx), which is the point index list of the current LOD.

[0515] If aps_extension_present is 1, geom_tree_type is 1, and attr_canonical_order_enabled is 1, CanonicalLodSubsampling is set to 1. Otherwise, CanonicalLodSubsampling is set to 0.

[0516] Periodic subsampling produces a subsampled output detail level by sampling all points within the sampling period at the input detail level.

[0517] When CanonicalLodSubsampling is 0, periodic subsampling produces subsampled output detail levels as follows:

[0518] The subsampling period for the current detail level is the subsampling period (subsamplingPeriod).

[0519] samplingPeriod := 2 + lod_sampling_period_minus2[Lvl]

[0520] Input points are assigned to output detail levels or refinement lists based on the remainder of the index within the input detail level divided by the sampling period.

[0521] OutLodPtCnt = outRfmtPtCnt = 0

[0522] for (i = 0; i < InLodPtCnt; i++) {

[0523] if (i % samplingPeriod)

[0524] OutLodPtIdx[OutLodPtCnt++] = InLodPtIdx[i]

[0525] else

[0526] OutRfmtPtIdx[outRfmtPtCnt++] = InLodPtIdx[i]

[0527] }

[0528] Standard order-based periodic sampling can be performed by including periodic sampling in the decoder.

[0529] Canonical-order-based periodic sampling can be performed when CanonicalLodSubsampling is 1 and dist_sampling_skip_flag is 0. The input index list corresponding to the current LOD index can be sorted in canonical order. If the index list is already sorted in canonical order, sorting can be omitted. Afterwards, periodic sampling can be performed sequentially on the sorted index list. At this time, the sampling period may be included in the bitstream and transmitted from the encoder. The sampling period may have a different value for each LOD index. As an example of the canonical-order-based periodic sampling method, if the remainder of the index included in the current index list divided by the sampling period is 0, the index corresponding to the corresponding order can be sampled and added to the upper LOD index list, OutRfmtPtIdx. In addition, indices with a non-zero remainder can be added to the point index list of the current LOD, OutLodPtIdx.

[0530] When CanonicalLodSubsampling is 1 and dist_sampling_skip_flag is 0, canonical order periodic subsampling can produce subsampled output detail levels in the following way:

[0531] The sampling period for the current detail level is subsamplingPeriod.

[0532] samplingPeriod := (Lv1==0 ? 1 : canonical_samplingPeriod[Lvl-1]) * (2 +

[0533] lod_sampling_period_minus2[Lvl])

[0534] Input points are assigned to output detail levels or refinement lists based on the remainder of their index within the input detail level divided by the sampling period.

[0535] OutLodPtCnt = outRfmtPtCnt = 0

[0536] for (i = 0; i < InLodPtCnt; i++) {

[0537] if (InLodPtIdx[i] % samplingPeriod)

[0538] OutLodPtIdx[OutLodPtCnt++] = InLodPtIdx[i]

[0539] else

[0540] OutRfmtPtIdx[outRfmtPtCnt++] = InLodPtIdx[i]

[0541] }

[0542] canonical_samplingPeriod[Lvl] = samplingPeriod

[0543] Periodic sampling using distance-based sampling omission can be performed as part of the periodic subsampling of the decoder.

[0544] The distance-based sampling skipping method proposed in the embodiments can be performed when CanonicalLodSubsampling is 1 and dist_sampling_skip_flag is 1. dist_sampling_skip_flag is a flag transmitted from the encoder as included in the bitstream and may have been transmitted in units of frames or slices. In addition, distance information used for sampling skipping may also be included in the bitstream and transmitted from the encoder. The decoder can ultimately calculate the sampling skip distance based on the distance information for sampling skipping and the LOD index. In the proposed method, the distance between the point corresponding to the previously sampled index and the point corresponding to the current index to be sampled is measured, and if the measured distance is smaller than the sampling skip distance, sampling is not performed and an index is added to OutLodPtIdx. Conversely, if the measured distance is greater than the sampling skip distance, an index is added to OutRfmtPtIdx and the current point position is stored for the next distance measurement. Periodic sampling can be performed by repeating the above process until the last index. After sampling, OutLodPtIdx and OutRfmtPtIdx can be reordered from standard order to Moulton code order for nearest neighbor search.

[0545] When CanonicalLodSubsampling is 1 and dist_sampling_skip_flag is 1, distance-based canonical order periodic subsampling can produce subsampled output detail levels in the following way:

[0546] The sampling period for the current detail level is subsamplingPeriod.

[0547] samplingPeriod := 2 + lod_sampling_period_minus2[Lvl]

[0548] Input points are assigned to output detail levels or refinement lists based on the remainder of their index within the input detail level divided by the sampling period.

[0549] OutLodPtCnt = outRfmtPtCnt = 0

[0550] radius2 = 2 << ((lod_initial_dist_log2 + lod_dist_log2_offset + Lvl)<< 1)

[0551] InLodPtIdx[i] shall be sorted by canonical order before subsampling.

[0552] for (i = 0; i < InLodPtCnt; i++) {

[0553] if (i % samplingPeriod)

[0554] OutLodPtIdx [OutLodPtCnt++] = InLodPtIdx[i]

[0555] else {

[0556] dist2 = Norm2(AttrPos[InLodIdx[i]], prevAttrPos)

[0557] if ( dist2 < radius2 ) {

[0558] OutLodPtIdx [OutLodPtCnt++] = InLodPtIdx[i]

[0559] continue

[0560] }

[0561] OutRfmtPtIdx[outRfmtPtCnt++] = InLodPtIdx[i]

[0562] prevAttrPos = AttrPos[InLodIdx[i]]

[0563] }

[0564] }

[0565] The output LOD point indices (OutLodPtIdx[i]) and output refinement point indices (OutRfmtPtIdx[i]) are sorted in Moulton code order after subsampling.

[0566] Figure 29 shows an encoding method according to embodiments.

[0567] The encoding method according to the embodiments includes a step of encoding geometry data of point cloud data (S2910); and / or a step of encoding attribute data of point cloud data (S2920).

[0568] Referring to FIGS. 13, 14, and 17, the step of encoding attribute data (S2920) includes generating a level of detail (LoD) based on points of point cloud data, and generating the LoD may include generating a second level by subsampling one or more points of a first level. A level index of the second level may have a value greater than a level index of the first level. The first level may mean a finer level than the second level, and the second level may mean a coarse level than the first level. In one embodiment, the first level may mean the finest level that includes all geometries.

[0569] Referring to FIG. 14, subsampling is performed based on a sampling period and a reference distance, and the reference distance may represent a minimum distance between sampled points. One or more points of the first level may be subsampled by a sampling period according to a point index, and a reference distance, which is a minimum distance between sampled points, may be applied. According to embodiments, if a point in a current sampling period is located within a reference distance from a point sampled in a previous sampling period, subsampling may be omitted in the current sampling period and the next sampling period may be moved. In addition, if a point in a next sampling period is located outside a reference distance from a point sampled in a previous sampling period, subsampling may be performed in the next sampling period. If a point in a next sampling period is located within a reference distance from a point sampled in a previous sampling period, subsampling may be omitted in the next sampling period and the next sampling period may be moved.

[0570] Referring to FIG. 14 and the like, according to embodiments, when a first point is subsampled in a first sampling period, and a second point within a subsequent sampling period of the first sampling period is located within a reference distance from the first point, subsampling of the second point may be omitted. In addition, when the second point within a subsequent sampling period of the first sampling period is located outside the reference distance from the first point, the second point may be subsampled.

[0571] And subsampling includes sorting one or more points of the first level based on a standard order other than the Moulton code, where the standard order may be an order of points output by decoding the geometry data.

[0572] The encoding method can be performed by an encoding device (encoder). The encoding device includes a memory; and at least one processor connected to the memory; and the at least one processor can be configured to: encode geometry data of point cloud data; and encode attribute data of the point cloud data.

[0573] The embodiments further include a computer-readable storage medium storing a bitstream generated by the method according to FIG. 29.

[0574] Embodiments further include a method comprising: obtaining a bitstream for point cloud data, the bitstream being generated based on a step of encoding geometry data of the point cloud data; and a step of encoding attribute data of the point cloud data; and transmitting data including the bitstream.

[0575] Figure 30 shows a decryption method according to embodiments.

[0576] In another embodiment, the decoding method according to the embodiments includes a step of decoding geometry data of point cloud data in a bitstream (S3010); and / or a step of decoding attribute data of point cloud data (S3020).

[0577] Referring to FIG. 14, the step of decoding attribute data (S3020) includes generating a level of detail (LoD) based on points of point cloud data, and generating the LoD may include generating a second level by subsampling one or more points of a first level. A level index of the second level may have a value greater than a level index of the first level. The first level may mean a finer level than the second level, and the second level may mean a coarse level than the first level. In one embodiment, the first level may mean the finest level that includes all geometries.

[0578] Referring to FIG. 14, subsampling is performed based on a sampling period and a reference distance, and the reference distance may represent a minimum distance between sampled points. One or more points of the first level may be subsampled by a sampling period according to a point index, and a reference distance, which is a minimum distance between sampled points, may be applied. According to embodiments, if a point in a current sampling period is located within a reference distance from a point sampled in a previous sampling period, subsampling may be omitted in the current sampling period and the next sampling period may be moved. In addition, if a point in a next sampling period is located outside a reference distance from a point sampled in a previous sampling period, subsampling may be performed in the next sampling period. If a point in a next sampling period is located within a reference distance from a point sampled in a previous sampling period, subsampling may be omitted in the next sampling period and the next sampling period may be moved.

[0579] Referring to FIG. 14 and the like, according to embodiments, when a first point is subsampled in a first sampling period, and a second point within a subsequent sampling period of the first sampling period is located within a reference distance from the first point, subsampling of the second point may be omitted. In addition, when the second point within a subsequent sampling period of the first sampling period is located outside the reference distance from the first point, the second point may be subsampled.

[0580] And subsampling includes sorting one or more points of the first level based on a standard order other than the Moulton code, where the standard order may be an order of points output by decoding the geometry data.

[0581] Referring to sampling_skip_dist in FIGS. 20 to 30, the bitstream may include information regarding a reference distance. Alternatively, the reference distance may be derived based on distance values ​​of one or more points.

[0582] And referring to sampling_skip_dist_enabled in FIGS. 20 to 30, the bitstream may include information indicating whether subsampling is performed based on a reference distance. In addition, the reference distance may be set to vary depending on the level of LOD, depending on the level index of the LOD.

[0583] The decryption method may be performed by a decryption device (decoder). The decryption device includes a memory; and at least one processor connected to the memory; and the at least one processor may be configured to: decode geometry data of point cloud data in a bitstream; and decode attribute data of the point cloud data.

[0584] The PCC encoding method, PCC decoding method, and signaling method of the above-described embodiments can provide the following effects.

[0585] The compression efficiency of the lifting transform can be improved by using distance to omit sampling for points densely located within a specific space with the same reflectivity in a spinning lidar point cloud. In particular, the omitted points generate a relatively small residual signal, allowing the point cloud to be compressed with fewer bits for the same error.

[0586] Accordingly, the transmission method / device according to the embodiments can efficiently compress point cloud data to transmit the data, and by transmitting signaling information for this, the reception method / device according to the embodiments can also efficiently decode / restore point cloud data.

[0587] The operation of the transmitting and receiving device according to the above-described embodiments can be explained in combination with the point cloud compression processing process below.

[0588]

[0589] The embodiments have been described in terms of methods and / or devices, and the descriptions of methods and devices may be applied complementarily.

[0590] For the convenience of explanation, each drawing has been described separately, but it is also possible to design a new embodiment by combining the embodiments described in each drawing. In addition, designing a computer-readable recording medium having a program recorded thereon for executing the previously described embodiments, as needed by a person skilled in the art, also falls within the scope of the embodiments. The devices and methods according to the embodiments are not limited to the configurations and methods of the embodiments described above, but the embodiments may be configured by selectively combining all or part of the embodiments so that various modifications can be made. Although preferred embodiments of the embodiments have been illustrated and described, the embodiments are not limited to the specific embodiments described above, and various modifications can be made by a person skilled in the art to which the present invention pertains without departing from the gist of the embodiments claimed in the claims, and such modifications should not be understood individually from the technical idea or prospect of the embodiments.

[0591] The various components of the devices of the embodiments may be implemented by hardware, software, firmware, or a combination thereof. The various components of the embodiments may be implemented by a single chip, for example, a single hardware circuit. According to embodiments, the components according to the embodiments may be implemented by separate chips. According to embodiments, at least one of the components of the devices of the embodiments may be configured with one or more processors capable of executing one or more programs, and the one or more programs may perform, or include instructions for performing, one or more of the operations / methods according to the embodiments. The executable instructions for performing the methods / operations of the devices of the embodiments may be stored in non-transitory CRMs or other computer program products configured to be executed by one or more processors, or may be stored in temporary CRMs or other computer program products configured to be executed by one or more processors. In addition, the memory according to the embodiments may be used as a concept including not only volatile memory (e.g., RAM, etc.), but also non-volatile memory, flash memory, PROM, etc. Additionally, it may include implementations in the form of carrier waves, such as transmissions via the Internet. Furthermore, processor-readable recording media may be distributed across network-connected computer systems, allowing processor-readable code to be stored and executed in a distributed manner.

[0592] In this document, “ / ” and “,” are interpreted as “and / or”. For example, “A / B” is interpreted as “A and / or B”, and “A, B” is interpreted as “A and / or B”. Additionally, “A / B / C” means “at least one of A, B, and / or C”. Also, “A, B, C” means “at least one of A, B, and / or C”. Additionally, “or” in this document is interpreted as “and / or”. For example, “A or B” can mean 1) “A” only, 2) “B” only, or 3) “A and B”. In other words, “or” in this document can mean “additionally or alternatively”.

[0593] Terms such as "first," "second," etc. may be used to describe various components of the embodiments. However, the various components according to the embodiments should not be interpreted as limited by these terms. These terms are merely used to distinguish one component from another. For example, a first user input signal may be referred to as a "second user input signal." Similarly, a second user input signal may be referred to as a "first user input signal." The use of these terms should be interpreted as not departing from the scope of the various embodiments. Although "first user input signal" and "second user input signal" are both user input signals, they do not mean the same user input signals unless the context clearly indicates otherwise.

[0594] The terminology used to describe the embodiments is for the purpose of describing particular embodiments and is not intended to be limiting of the embodiments. As used in the description of the embodiments and in the claims, the singular is intended to include the plural unless the context clearly dictates otherwise. The expressions “and / or” are used to mean all possible combinations of terms. The expression “includes” describes the presence of features, numbers, steps, elements, and / or components, but does not mean that additional features, numbers, steps, elements, and / or components are not included. Conditional expressions such as “if” or “when” used to describe the embodiments are not intended to be limited to only optional cases. When a specific condition is satisfied, a related action is performed in response to a specific condition, or a related definition is intended to be interpreted.

[0595] Additionally, the operations according to the embodiments described in this document may be performed by a transceiver device including a memory and / or a processor according to the embodiments. The memory may store programs for processing / controlling the operations according to the embodiments, and the processor may control various operations described in this document. The processor may be referred to as a controller, etc. The operations according to the embodiments may be performed by firmware, software, and / or a combination thereof, and the firmware, software, and / or a combination thereof may be stored in the processor or in the memory.

[0596] Meanwhile, the operations according to the embodiments described above may be performed by a transmitting device and / or a receiving device according to the embodiments. The transmitting / receiving device may include a transmitting / receiving unit for transmitting and receiving media data, a memory for storing instructions (program code, algorithm, flowchart, and / or data) for a process according to the embodiments, and a processor for controlling the operations of the transmitting / receiving device.

[0597] The processor may be referred to as a controller or the like, and may correspond to, for example, hardware, software, and / or a combination thereof. The operations according to the above-described embodiments may be performed by the processor. Furthermore, the processor may be implemented as an encoder / decoder or the like for the operations of the above-described embodiments.

[0598]

[0599] As described above, the relevant contents have been described in the best form for carrying out the embodiments.

[0600]

[0601] As described above, the embodiments may be applied in whole or in part to a point cloud data transmission and reception device and system.

[0602] Those skilled in the art may make various changes or modifications to the embodiments within the scope of the embodiments.

[0603] Embodiments may include modifications / changes, which do not depart from the scope of the claims and their equivalents.

Claims

1. A step of decoding geometry data of point cloud data in a bitstream; and A step of decoding attribute data of the above point cloud data; comprising; How to decrypt.

2. In paragraph 1, The step of decoding the above attribute data is: Including generating LoD (level of Detail) based on points of the above point cloud data, Generating the above LoD includes generating a second level by subsampling one or more points of the first level. How to decrypt.

3. In paragraph 2, The above subsampling is performed based on the sampling period and reference distance, The above reference distance represents the minimum distance between sampled points. How to decrypt.

4. In paragraph 3, The above subsampling is, Subsample the first point in the first sampling period, If the second point within the next sampling period of the first sampling period is located within the reference distance from the first point, subsampling is omitted, Including subsampling when the second point within the next sampling period of the first sampling period is located outside the reference distance from the first point. How to decrypt.

5. In paragraph 3, The above bitstream contains information about the reference distance, or The above reference distance is derived based on the distance values ​​of one or more points. How to decrypt.

6. In paragraph 3, The bitstream includes information indicating whether the subsampling is performed based on the reference distance. How to decrypt.

7. In paragraph 3, The above reference distance is set to vary according to the index of the LOD. How to decrypt.

8. In paragraph 3, The subsampling comprises sorting the one or more points based on a standard order other than the Moulton code, The above standard order is the order of points output by decoding the above geometry data. How to decrypt.

9. Memory; and At least one processor connected to the memory; wherein the at least one processor comprises: Decoding geometry data of point cloud data in the bitstream; and Decoding attribute data of the above point cloud data; configured to do so, Decryption device.

10. A step of encoding the geometry data of the point cloud data; and A step of encoding attribute data of the above point cloud data; comprising; Encoding method.

11. In paragraph 10, The step of encoding the above attribute data is: Including generating LoD (level of Detail) based on points of the above point cloud data, Generating the above LoD includes generating a second level by subsampling one or more points of the first level. Encoding method.

12. In paragraph 11, The above subsampling is performed based on the sampling period and reference distance, The above reference distance represents the minimum distance between sampled points. Encoding method.

13. Memory; and At least one processor connected to the memory; wherein the at least one processor comprises: Encoding the geometry data of point cloud data; and Encoding attribute data of the above point cloud data; configured to do so; Decryption device.

14. A computer-readable storage medium storing a bitstream generated by the method according to Article 10.

15. Step of obtaining bitstream for point cloud data; The bitstream is generated based on the steps of encoding geometry data of the point cloud data; and encoding attribute data of the point cloud data; and A method comprising the step of transmitting data including the bitstream.

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