Point cloud encoding method, point cloud decoding method, encoder, decoder, code stream, and storage medium

Abstract

Embodiments of the present application provide a point cloud encoding method and a point cloud decoding method, which can improve the attribute encoding and decoding efficiency of a point cloud, thereby improving the encoding and decoding performance of the point cloud. The point cloud decoding method comprises: parsing a code stream and determining a region-adaptive hierarchical transform (RAHT) encoding mode corresponding to a current layer and attribute encoding information corresponding to a node in the current layer; an encoder encoding attribute information of the node in the current layer by means of at least one RAHT encoding mode, determining at least one encoding cost corresponding to the node, and on the basis of the at least one encoding cost corresponding to the node, determining an RAHT encoding mode corresponding to the current layer; and on the basis of the RAHT encoding mode corresponding to the current layer, decoding and reconstructing the attribute encoding information corresponding to the node in the current layer, and determining reconstruction attribute information corresponding to the node.

Description

Point cloud encoding and decoding method, encoder, decoder, code stream and storage medium Technical Field

[0001] The embodiments of the present application relate to the field of point cloud compression technology, and in particular to a point cloud encoding and decoding method, encoder, decoder, code stream, and storage medium. Background Art

[0002] In the geometry-based Point Cloud Compression (G-PCC) codec framework or video-based Point Cloud Compression (V-PCC) codec framework provided by the Moving Picture Experts Group (MPEG), the geometric information and attribute information of the point cloud are encoded separately.

[0003] At present, attribute information encoding mainly targets the encoding of color information. In color information encoding, there are three main transformation methods, including: Predicting Transform (PT) and Lifting Transform (LT) that rely on the level of detail (LOD) division, and Region Adaptive Hierarchal Transform (RAHT) based on octree.

[0004] Among them, for RAHT encoding and decoding, when the RAHT prediction transform encoding and decoding conditions are met, the RAHT encoding and decoding layer that uses the RAHT inter-frame prediction transform mode for encoding and decoding is specified in the point cloud to be encoded and decoded. For the RAHT encoding and decoding layer below, only the RAHT intra-frame prediction encoding and decoding method is used. In the current RAHT coding scheme, whether the RAHT prediction transform encoding and decoding conditions are met is determined based on the number of neighboring nodes of the current node. If the RAHT prediction transform encoding and decoding conditions are met, the attribute information of the current node is RAHT predicted transform encoded. Otherwise, only the attribute information of the current node is RAHT transformed. This encoding and decoding method only utilizes the spatial correlation of each node, especially the neighborhood geometric space correlation, to determine the RAHT encoding and decoding method for the attribute information of each node, resulting in low encoding and decoding efficiency of the attribute information.

[0005] Summary of the Invention

[0006] The embodiments of the present application provide a point cloud encoding and decoding method, encoder, decoder, code stream and storage medium, which can improve the attribute encoding and decoding efficiency of the point cloud, thereby improving the encoding and decoding performance of the point cloud.

[0007] The technical solution of the embodiment of the present application can be implemented as follows:

[0008] In a first aspect, an embodiment of the present application provides a decoding method, applied to a decoder, the method comprising:

[0009] Parsing a bitstream to determine a RAHT coding mode corresponding to a current layer and attribute coding information corresponding to a node in the current layer; the RAHT coding mode corresponding to the current layer is determined by an encoder encoding attribute information of a node in the current layer using at least one region adaptive layered transform (RAHT) coding mode, and determining at least one coding cost corresponding to the node based on the at least one coding cost corresponding to the node;

[0010] Based on the RAHT coding mode corresponding to the current layer, attribute coding information corresponding to the node in the current layer is decoded and reconstructed to determine the reconstructed attribute information corresponding to the node.

[0011] In a second aspect, an embodiment of the present application provides an encoding method, applied to an encoder, the method comprising:

[0012] Encoding attribute information of a node in a current layer using at least one region adaptive layered transform (RAHT) coding mode, and determining at least one coding cost and at least one candidate attribute coding information corresponding to the node;

[0013] Determining a RAHT coding mode corresponding to the current layer based on at least one coding cost corresponding to the node, and determining attribute coding information corresponding to the node from the at least one candidate attribute coding information;

[0014] A code stream is generated based on the RAHT coding mode corresponding to the current layer and the attribute coding information corresponding to the node.

[0015] In a third aspect, an embodiment of the present application provides a decoder, including:

[0016] a parsing portion configured to parse a bitstream and determine a RAHT coding mode corresponding to a current layer and attribute coding information corresponding to a node in the current layer; the RAHT coding mode corresponding to the current layer is determined by an encoder encoding attribute information of a node in the current layer using at least one region adaptive layered transform (RAHT) coding mode, and determining at least one coding cost corresponding to the node based on the at least one coding cost corresponding to the node;

[0017] The decoding and reconstruction part is configured to decode and reconstruct the attribute coding information corresponding to the node in the current layer based on the RAHT coding mode corresponding to the current layer, and determine the reconstructed attribute information corresponding to the node.

[0018] In a fourth aspect, an embodiment of the present application provides an encoder, including:

[0019] The encoding part is configured to encode attribute information of a node in a current layer by using at least one region adaptive layered transform (RAHT) coding mode, and determine at least one coding cost and at least one candidate attribute coding information corresponding to the node;

[0020] a determining part configured to determine a RAHT coding mode corresponding to the current layer based on at least one coding cost corresponding to the node, and determine attribute coding information corresponding to the node from at least one candidate attribute coding information;

[0021] The generating part is configured to generate a code stream based on the RAHT coding mode corresponding to the current layer and the attribute coding information corresponding to the node.

[0022] In a fourth aspect, an embodiment of the present application provides an encoder, comprising a first memory and a first processor;

[0023] The first memory is used to store a computer program that can be run on the first processor;

[0024] The first processor is configured to execute the method according to the second aspect when running the computer program.

[0025] In a fifth aspect, an embodiment of the present application provides a decoder, the decoder comprising

[0026] In a sixth aspect, an embodiment of the present application provides a decoder, the decoder comprising a second memory and a second processor;

[0027] The second memory is used to store a computer program that can be run on the second processor;

[0028] The second processor is configured to execute the method according to the first aspect when running the computer program.

[0029] In a seventh aspect, an embodiment of the present application provides a code stream, which is generated by bit encoding based on information to be encoded; wherein the information to be encoded includes at least: a RAHT coding mode corresponding to the current layer and attribute coding information corresponding to the node in the current layer; the RAHT coding mode corresponding to the current layer is determined based on at least one coding cost corresponding to the node in the current layer; and the at least one coding cost corresponding to the node in the current layer is determined by encoding the attribute information of the node in the current layer through at least one RAHT coding mode.

[0030] In an eighth aspect, an embodiment of the present application provides a storage medium storing a computer program, which, when executed, implements the method described in the first aspect or the method described in the second aspect.

[0031] The embodiment of the present application provides a point cloud encoding and decoding method, encoder, decoder, code stream and storage medium. In the embodiment of the present application, the decoder decodes and reconstructs the attribute coding information corresponding to the nodes in the current layer according to the RAHT coding mode transmitted by the encoder, and determines the reconstructed attribute information corresponding to the nodes. Since the RAHT coding mode corresponding to the current layer is that the encoder comprehensively considers the attribute distribution characteristics and spatial distribution characteristics of each node, encodes each node in the current layer through at least one RAHT coding method, determines at least one coding cost corresponding to each node, and determines the optimal coding mode for the current layer based on the at least one coding cost corresponding to each node. The decoder selects a decoding mode corresponding to the RAHT coding mode corresponding to the current layer for decoding, thereby decoding the attribute information of the current layer according to the optimal RAHT coding mode corresponding to the current layer transmitted by the encoder. In this way, by adaptively selecting the optimal coding and decoding mode from multiple coding and decoding modes, the RAHT attribute coding efficiency and the decoding efficiency of the point cloud attribute information are improved, thereby improving the point cloud decoding performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG1A is a schematic diagram of a three-dimensional point cloud image;

[0033] FIG1B is a partially enlarged view of a three-dimensional point cloud image;

[0034] FIG2A is a schematic diagram of six viewing angles of a point cloud image;

[0035] FIG2B is a schematic diagram of a data storage format corresponding to a point cloud image;

[0036] FIG3 is a schematic diagram of a network architecture for point cloud encoding and decoding;

[0037] FIG4A is a schematic diagram of a composition framework of a G-PCC encoder;

[0038] FIG4B is a schematic diagram of a composition framework of a G-PCC decoder;

[0039] FIG5A is a schematic diagram of a low plane position in the Z-axis direction;

[0040] FIG5B is a schematic diagram of a high plane position in the Z-axis direction;

[0041] FIG6 is a schematic diagram of a node coding sequence;

[0042] FIG7A is a schematic diagram of plane identification information;

[0043] FIG7B is a schematic diagram of another type of planar identification information;

[0044] FIG8 is a schematic diagram of sibling nodes of a current node;

[0045] Figure 9 is a schematic diagram of the intersection of a laser radar and a node;

[0046] FIG10 is a schematic diagram of neighborhood nodes at the same partition depth and the same coordinates;

[0047] FIG11 is a schematic diagram of a current node being located at a low plane position of a parent node;

[0048] FIG12 is a schematic diagram showing a current node located at a high plane position of a parent node;

[0049] FIG13 is a schematic diagram of predictive coding of planar position information of a laser radar point cloud;

[0050] FIG14 is a schematic diagram of IDCM encoding;

[0051] FIG15 is a schematic diagram of coordinate transformation of a rotating laser radar to obtain a point cloud;

[0052] FIG16 is a schematic diagram of predictive coding in the X-axis or Y-axis direction;

[0053] FIG17A is a schematic diagram showing an angle of the Y plane predicted by the horizontal azimuth angle;

[0054] FIG17B is a schematic diagram showing an angle of the X-plane predicted by the horizontal azimuth angle;

[0055] FIG18 is another schematic diagram of predictive coding in the X-axis or Y-axis direction;

[0056] FIG19A is a schematic diagram of three intersection points included in a sub-block;

[0057] FIG19B is a schematic diagram of a triangular facet set fitted using three intersection points;

[0058] FIG19C is a schematic diagram of upsampling of a triangle face set;

[0059] FIG20 is a schematic diagram of a distance-based LOD construction process;

[0060] FIG21 is a schematic diagram of a visualization result of an LOD generation process;

[0061] FIG22 is a schematic diagram of an encoding process for attribute prediction;

[0062] FIG23 is a schematic diagram of the composition of a pyramid structure;

[0063] FIG24 is a schematic diagram showing the composition of another pyramid structure;

[0064] FIG25 is a schematic diagram of an LOD structure for inter-layer nearest neighbor search;

[0065] FIG26 is a schematic diagram of a nearest neighbor search structure based on spatial relationships;

[0066] FIG27A is a schematic diagram of a coplanar spatial relationship;

[0067] FIG27B is a schematic diagram of a coplanar and colinear spatial relationship;

[0068] FIG27C is a schematic diagram of a spatial relationship of coplanarity, colinearity, and copointness;

[0069] FIG28 is a schematic diagram of inter-layer prediction based on fast search;

[0070] FIG29 is a schematic diagram of an LOD structure for nearest neighbor search within an attribute layer;

[0071] FIG30 is a schematic diagram of intra-layer prediction based on fast search;

[0072] FIG31 is a block-based neighborhood search structure diagram;

[0073] FIG32 is a schematic diagram of an encoding process of a lifting transform;

[0074] FIG33 is a schematic diagram of a RAHT transformation structure;

[0075] FIG34 is a schematic diagram of a RAHT transformation process along the x, y, and z directions;

[0076] FIG35A is a schematic diagram of a RAHT forward transformation process;

[0077] FIG35B is a schematic diagram of a RAHT inverse transformation process;

[0078] FIG36 is a schematic diagram of the structure of an attribute coding block;

[0079] FIG37 is a schematic diagram of the overall process of RAHT attribute prediction transform coding;

[0080] FIG38 is a schematic diagram of a neighborhood prediction relationship of a current block;

[0081] FIG39 is a schematic diagram of a calculation process of an attribute transformation coefficient;

[0082] FIG40 is a schematic diagram of a RAHT attribute inter-frame prediction coding structure;

[0083] FIG41 is a schematic diagram of a flow chart of a point cloud encoding method provided in an embodiment of the present application;

[0084] FIG42 is a schematic diagram of a flow chart of a point cloud decoding method provided in an embodiment of the present application;

[0085] FIG43 is a schematic diagram of the structure of an encoder provided in an embodiment of the present application;

[0086] FIG44 is a schematic diagram of a specific hardware structure of an encoder provided in an embodiment of the present application;

[0087] FIG45 is a schematic diagram of the structure of a decoder provided in an embodiment of the present application;

[0088] FIG46 is a schematic diagram of a specific hardware structure of a decoder provided in an embodiment of the present application;

[0089] Figure 47 is a schematic diagram of the composition structure of a coding and decoding system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0090] In order to enable a more detailed understanding of the features and technical contents of the embodiments of the present application, the implementation of the embodiments of the present application is described in detail below with reference to the accompanying drawings. The attached drawings are for reference only and are not used to limit the embodiments of the present application.

[0091] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein are for the purpose of describing the embodiments of this application only and are not intended to limit this application.

[0092] In the following description, reference is made to “some embodiments”, which describes a subset of all possible embodiments, but it will be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0093] It should also be pointed out that the terms "first\second\third" involved in the embodiments of the present application are only used to distinguish similar objects and do not represent a specific ordering of the objects. It can be understood that "first\second\third" can be interchanged with a specific order or sequence where permitted, so that the embodiments of the present application described here can be implemented in an order other than that illustrated or described here.

[0094] Point cloud is a three-dimensional representation of the surface of an object. Point cloud (data) of the surface of an object can be collected through acquisition equipment such as photoelectric radar, lidar, laser scanner, and multi-view camera.

[0095] A point cloud is a set of irregularly distributed discrete points in space that express the spatial structure and surface properties of a three-dimensional object or scene. Figure 1A shows a three-dimensional point cloud image and Figure 1B shows a magnified partial view of the three-dimensional point cloud image. It can be seen that the point cloud surface is composed of densely distributed points.

[0096] Two-dimensional images contain information at every pixel, and their distribution is regular, so there's no need to record their location information. However, the distribution of points in a point cloud in three-dimensional space is random and irregular, so recording the location of each point in space is necessary to fully represent a point cloud. Similar to two-dimensional images, each location in the acquisition process has corresponding attribute information, typically an RGB color value, which reflects the object's color. For point clouds, in addition to color information, each point's corresponding attribute information often includes reflectance values, which reflect the surface texture of the object. Therefore, point cloud data typically includes geometric information consisting of three-dimensional position information, three-dimensional color information, and attribute information consisting of one-dimensional reflectance information. Points in a point cloud can include both position information and attribute information. For example, the position information of a point can be its three-dimensional coordinate information (x, y, z). The position information of a point can also be referred to as its geometric information. For example, the attribute information of a point can include color information (three-dimensional color information) and / or reflectance (one-dimensional reflectance information r). For example, the color information can be information in any color space, such as RGB information. Here, R represents red (Red, R), G represents green (Green, G), and B represents blue (Blue, B). For another example, the color information can be luminance and chrominance (YCbCr, YUV) information. Here, Y represents brightness (Luma), Cb (U) represents the blue color difference, and Cr (V) represents the red color difference.

[0097] For example, a point cloud generated using laser measurement principles can include both its 3D coordinate information and its reflectivity. For another example, a point cloud generated using photogrammetry principles can include both its 3D coordinate information and its 3D color information. For another example, a point cloud generated using a combination of laser measurement and photogrammetry principles can include both its 3D coordinate information, its reflectivity value, and its 3D color information.

[0098] Figures 2A and 2B show a point cloud image and its corresponding data storage format. Figure 2A provides six viewing angles of the point cloud image, while Figure 2B consists of a file header and data. The header includes the data format, data representation type, the total number of points in the point cloud, and the content represented by the point cloud. For example, the point cloud is in ".ply" format, represented by ASCII code, with a total of 207,242 points. Each point has 3D coordinate information (x, y, z) and 3D color information (r, g, b).

[0099] Point clouds can be divided into the following categories according to the acquisition method:

[0100] Static point cloud: the object is stationary and the device that acquires the point cloud is also stationary;

[0101] Dynamic point cloud: The object is moving, but the device that obtains the point cloud is stationary;

[0102] Dynamic point cloud acquisition: The device used to acquire the point cloud is in motion.

[0103] For example, point clouds can be divided into two categories according to their usage:

[0104] Category 1: Machine perception point cloud, which can be used in scenarios such as autonomous navigation systems, real-time inspection systems, geographic information systems, visual sorting robots, and disaster relief robots;

[0105] Category 2: Human eye perception point cloud, which can be used in point cloud application scenarios such as digital cultural heritage, free viewpoint broadcasting, 3D immersive communication, and 3D immersive interaction.

[0106] Point clouds can flexibly and conveniently express the spatial structure and surface properties of three-dimensional objects or scenes. Moreover, since point clouds are obtained by directly sampling real objects, they can provide a strong sense of reality while ensuring accuracy. Therefore, they are widely used, including virtual reality games, computer-aided design, geographic information systems, automatic navigation systems, digital cultural heritage, free viewpoint broadcasting, three-dimensional immersive remote presentation, and three-dimensional reconstruction of biological tissues and organs.

[0107] Point clouds are primarily collected through computer generation, 3D laser scanning, and 3D photogrammetry. Computers can generate point clouds of virtual 3D objects and scenes; 3D laser scanning can obtain point clouds of static real-world 3D objects or scenes, generating millions of point clouds per second; and 3D photogrammetry can obtain point clouds of dynamic real-world 3D objects or scenes, generating tens of millions of point clouds per second. These technologies reduce the cost and time required to acquire point cloud data while improving data accuracy. While changes in point cloud data acquisition methods have made it possible to acquire large amounts of point cloud data, the processing of this massive amount of 3D point cloud data is facing bottlenecks due to storage space and transmission bandwidth constraints, as application demands grow.

[0108] For example, taking a point cloud video with a frame rate of 30 frames per second (fps), each frame contains 700,000 points, and each point has coordinate information (xyz, float) and color information (RGB, uchar). Therefore, the data volume of a 10-second point cloud video is approximately 0.7 million × (4 bytes × 3 + 1 byte × 3) × 30 fps × 10 seconds = 3.15 GB, where 1 byte is 10 bits. For a 1280 × 720 2D video with a YUV sampling format of 4:2:0 and a frame rate of 24 fps, the data volume for 10 seconds is approximately 1280 × 720 × 12 bits × 24 fps × 10 seconds ≈ 0.33 GB. The data volume of a 10-second two-view 3D video is approximately 0.33 × 2 = 0.66 GB. This shows that the data volume of a point cloud video far exceeds that of 2D and 3D videos of the same length. Therefore, in order to better realize data management, save server storage space, and reduce the transmission traffic and transmission time between the server and the client, point cloud compression has become a key issue in promoting the development of the point cloud industry.

[0109] That is to say, since the point cloud is a collection of massive points, storing the point cloud not only consumes a lot of memory, but is also not conducive to transmission. There is also not enough bandwidth to support direct transmission of the point cloud at the network layer without compression. Therefore, the point cloud needs to be compressed.

[0110] Currently, the point cloud coding framework that can compress point clouds can be the geometry-based Point Cloud Compression (G-PCC) codec framework or the video-based Point Cloud Compression (V-PCC) codec framework provided by the Moving Picture Experts Group (MPEG), or the AVS-PCC codec framework provided by AVS. The G-PCC codec framework can be used to compress the first type of static point clouds and the third type of dynamically acquired point clouds, which can be based on the Point Cloud Compression Test Platform (Test Model Compression 13, TMC13). The V-PCC codec framework can be used to compress the second type of dynamic point clouds, which can be based on the Point Cloud Compression Test Platform (Test Model Compression 2, TMC2). Therefore, the G-PCC codec framework is also called the point cloud codec TMC13, and the V-PCC codec framework is also called the point cloud codec TMC2.

[0111] An embodiment of the present application provides a network architecture of a point cloud encoding and decoding system including a decoding method and an encoding method. FIG3 is a schematic diagram of a network architecture of a point cloud encoding and decoding system provided by an embodiment of the present application. As shown in FIG3 , the network architecture includes one or more electronic devices 13 to 1N and a communication network 01, wherein the electronic devices 13 to 1N can perform video interaction through the communication network 01. During the implementation process, the electronic device can be various types of devices with point cloud encoding and decoding functions. For example, the electronic device can include a mobile phone, a tablet computer, a personal computer, a personal digital assistant, a navigator, a digital phone, a video phone, a television, a sensor device, a server, etc., which is not limited by the embodiment of the present application. Among them, the decoder or encoder in the embodiment of the present application can be the above-mentioned electronic device.

[0112] Among them, the electronic device in the embodiment of the present application has a point cloud encoding and decoding function, generally including a point cloud encoder (ie, encoder) and a point cloud decoder (ie, decoder).

[0113] The following describes the related technologies using the G-PCC encoding and decoding framework as an example.

[0114] As you can understand, in the point cloud G-PCC codec framework, the point cloud data to be encoded is first divided into multiple slices through slice partitioning. In each slice, the geometric information of the point cloud and the attribute information corresponding to each point are encoded separately.

[0115] Figure 4A shows a schematic diagram of the G-PCC encoder architecture. As shown in Figure 4A, during the geometry encoding process, the geometric information is transformed so that the entire point cloud is contained within a bounding box. Quantization is then performed. This quantization step primarily serves a scaling purpose. Due to quantization rounding, the geometric information of some point clouds becomes identical. Parameters are then used to determine whether to remove duplicate points. This process of quantization and removing duplicate points is also known as voxelization. The bounding box is then partitioned into an octree or a prediction tree is constructed. During this process, arithmetic coding is performed on the points in the leaf nodes of the partition to generate a binary geometry bitstream. Alternatively, arithmetic coding is performed on the intersection points (vertices) generated by the partition (surface fitting is performed based on the intersection points) to generate a binary geometry bitstream. During the attribute encoding process, after the geometry encoding is completed and the geometric information is reconstructed, color conversion is performed to convert the color information (i.e., attribute information) from the RGB color space to the YUV color space. The reconstructed geometry information is then used to recolor the point cloud so that the unencoded attribute information corresponds to the reconstructed geometry information. Attribute encoding is mainly performed on color information. In the color information encoding process, there are two main transformation methods. One is the distance-based lifting transformation that relies on the level of detail (LOD) division, and the other is the direct region adaptive hierarchical transformation (RAHT). Both methods convert color information from the spatial domain to the frequency domain, obtain high-frequency coefficients and low-frequency coefficients through transformation, and finally quantize the coefficients. Then, the quantized coefficients are arithmetically encoded to generate a binary attribute bit stream.

[0116] Figure 4B shows a schematic diagram of the composition framework of a G-PCC decoder. As shown in Figure 4B, for the acquired binary bit stream, the geometric bit stream and attribute bit stream in the binary bit stream are first decoded independently. When decoding the geometric bit stream, the geometric information of the point cloud is obtained through arithmetic decoding-reconstruction of the octree / reconstruction of the prediction tree-reconstruction of the geometry-coordinate inverse conversion; when decoding the attribute bit stream, the attribute information of the point cloud is obtained through arithmetic decoding-inverse quantization-LOD partitioning / RAHT-color inverse conversion, and the point cloud data to be encoded (i.e., the output point cloud) is restored based on the geometric information and attribute information.

[0117] It should be noted that, as shown in FIG4A or FIG4B , the current geometric coding and decoding of G-PCC can be divided into octree-based geometric coding and decoding (marked by a dotted box) and prediction tree-based geometric coding and decoding (marked by a dotted box).

[0118] For Octree geometry encoding (OctGeomEnc), the octree-based geometry encoding includes: first, coordinate conversion of the geometric information so that all point clouds are contained in a Bounding Box. Then quantization is performed. This step of quantization mainly plays a role of scaling. Due to the quantization rounding, the geometric information of some points is the same. The parameters are used to decide whether to remove duplicate points. The process of quantization and removal of duplicate points is also called voxelization. Next, the Bounding Box is continuously divided into trees (such as octrees, quadtrees, binary trees, etc.) in the order of breadth-first traversal, and the placeholder code of each node is encoded. In related technologies, a company proposed an implicit geometric division method. First, the bounding box of the point cloud is calculated. Assume d x >d y >d z , the bounding box corresponds to a cuboid. When geometrically partitioning, the binary tree partitioning will be performed based on the x-axis to obtain two child nodes; until d is satisfied x =d y >d z When the conditions are met, the quadtree partitioning will be performed based on the x and y axes to obtain four child nodes; when d is finally satisfied x =d y =d z When the conditions are met, the octree partitioning will continue until the leaf node obtained by the partitioning is a 1×1×1 unit cube. The partitioning will stop and the points in the leaf node will be encoded to generate a binary code stream. In the process of binary tree / quadtree / octree partitioning, two parameters are introduced: K and M. Parameter K indicates the maximum number of binary tree / quadtree partitions before octree partitioning; parameter M is used to indicate that the minimum block side length corresponding to binary tree / quadtree partitioning is 2 M . At the same time, K and M must meet the following conditions: Assume d max =max(d x ,d y ,d z ), d min =min(d x ,d y ,d z ), parameter K satisfies: K ≥ d max -d min ; Parameter M satisfies: M≥d minThe reason why the parameters K and M meet the above conditions is that in the current G-PCC geometric implicit partitioning process, the priority of the partitioning method is binary tree, quadtree and octree. When the node block size does not meet the conditions of binary tree / quadtree, the node will be divided into octree until the minimum unit of leaf node is 1×1×1. The octree-based geometric information coding mode can effectively encode the geometric information of the point cloud by utilizing the correlation between adjacent points in space. However, for some relatively flat nodes or nodes with planar characteristics, the coding efficiency of the point cloud geometric information can be further improved by using plane coding.

[0119] Exemplarily, Figure 5A and Figure 5B provide a kind of plane position schematic diagram.Wherein, Figure 5A shows a kind of low plane position schematic diagram in the Z-axis direction, and Figure 5B shows a kind of high plane position schematic diagram in the Z-axis direction.As shown in Figure 5A, here (a), (a0), (a1), (a2), (a3) ​​all belong to the low plane position in the Z-axis direction. Taking (a) as an example, it can be seen that the four child nodes occupied in the current node are all located at the low plane position of the current node in the Z-axis direction, so it can be considered that the current node belongs to a Z plane and is a low plane in the Z-axis direction. Similarly, as shown in Figure 5B, here (b), (b0), (b1), (b2), (b3) all belong to the high plane position in the Z-axis direction. Taking (b) as an example, it can be seen that the four child nodes occupied in the current node are located at the high plane position of the current node in the Z-axis direction, so it can be considered that the current node belongs to a Z plane and is a high plane in the Z-axis direction.

[0120] Taking (a) in Figure 5A as an example, the efficiency of octree encoding and plane encoding is compared. Figure 6 provides a schematic diagram of the node encoding sequence, that is, node encoding is performed in the order of 0, 1, 2, 3, 4, 5, 6, and 7 as shown in Figure 6. Here, if octree encoding is used for (a) in Figure 5A, the placeholder information of the current node is represented as: 11001100. However, if plane encoding is used, first, an identifier must be encoded to indicate that the current node is a plane in the Z-axis direction. Secondly, if the current node is a plane in the Z-axis direction, the plane position of the current node must also be represented. Finally, only the placeholder information of the lower plane node in the Z-axis direction needs to be encoded (i.e., the placeholder information of the four child nodes 0, 2, 4, and 6). Therefore, encoding the current node based on plane encoding only requires 6 bits, which can reduce the representation by 2 bits compared to the related art octree encoding. Based on this analysis, plane encoding has significantly higher coding efficiency than octree encoding. Therefore, for an occupied node, if a plane encoding method is used in a certain dimension, it is first necessary to represent the plane identification (planarMode) and plane position (PlanePos) information of the current node in that dimension, and then encode the occupancy information of the current node based on the plane information of the current node. For example, FIG7A shows a schematic diagram of plane identification information. As shown in FIG7A, there is a low plane in the Z-axis direction; correspondingly, the value of the plane identification information is true (true) or 1, that is, planarMode_ Z = true; the plane position information is the low plane (low), that is, PlanePosition_ Z =low. FIG7B shows another schematic diagram of plane identification information. As shown in FIG7B, here it is not a plane in the Z-axis direction; correspondingly, the value of the plane identification information is false or 0, that is, planarMode_ Z =false.

[0121] It should be noted that for PlaneMode_ i :0 means the current node is not a plane in the i-axis direction, 1 means the current node is a plane in the i-axis direction. If the current node is a plane in the i-axis direction, then for PlanePosition_ i : 0 means the current node is a plane in the i-axis direction and the plane position is low, 1 means the current node is a high plane in the i-axis direction. Here, i represents the coordinate dimension, which can be the X-axis direction, Y-axis direction, or Z-axis direction, so i = 0, 1, 2.

[0122] In the G-PCC standard, to determine whether a node meets the conditions for planar coding and when the node meets the planar coding conditions, predictive coding of the planar identifier and planar position information of the node is required.

[0123] In the embodiments of the present application, there are three judgment conditions in the current G-PCC standard for determining whether a node meets the planar coding. The following will explain them in detail one by one.

[0124] First, judge according to the planar probability of the node in each dimension.

[0125] (1) Determine the local area density (local_node_density) of the current node;

[0126] (2) Determine the probability Prob(i) of the current node in each dimension.

[0127] When the local area density of the node is less than the threshold Th (for example, Th = 3), compare the planar probability Prob(i) of the current node in the three coordinate dimensions with the thresholds Th0, Th1, and Th2, where Th0 < Th1 < Th2 (for example, Th0 = 0.6, Th1 = 0.77, Th2 = 0.88). Here, Eligible i (i = 0, 1, 2) is used to represent whether planar coding is enabled in each dimension: Eligible i = Prob(i) >= threshold.

[0128] It should be noted that the threshold is adaptively changed. For example, when Prob(0) > Prob(1) > Prob(2), the settings of Eligible i are as follows: Eligible0 = Prob(0) >= Th0; Eligible1 = Prob(1) >= Th1; Eligible2 = Prob(2) >= Th2.

[0129] When Prob(1) > Prob(0) > Prob(2), the settings of Eligible i are as follows: Eligible0 = Prob(0) >= Th1; Eligible1 = Prob(1) >= Th0; Eligible2 = Prob(2) >= Th2.

[0130] Here, the update of Prob(i) is specifically as follows: Prob(i) new = (L × Prob(i) + δ(coded node)) / L + 1

[0131] Where L = 255; in addition, if the coded node is a plane, δ(coded node) is 1; otherwise, δ(coded node) is 0.

[0132] Here, the update of local_node_density is as follows: local_node_density new =local_node_density+4*numSiblings

[0133] Where local_node_density is initialized to 4, and numSiblings is the number of sibling nodes of the node. For example, FIG8 shows a schematic diagram of the sibling nodes of the current node. As shown in FIG8 , the current node is a node filled with slashes, and the nodes filled with grids are sibling nodes. Then, the number of sibling nodes of the current node is 5 (including the current node itself).

[0134] Second, determine whether the current layer nodes meet the plane coding requirements based on the point cloud density of the current layer.

[0135] The density of the current layer points is used to determine whether to perform planar coding on the nodes of the current layer. Assuming that the number of points in the current point cloud to be coded is pointCount, the number of points reconstructed by the inferred direct coding model (IDCM) coding is numPointCountRecon, and because the octree is coded based on the order of breadth-first traversal, the number of nodes to be coded in the current layer can be obtained as nodeCount. Then, the assumption to determine whether to start planar coding in the current layer is planarEligibleKOctreeDepth, specifically: planarEligibleK OctreeDepth = (pointCount-numPointCountRecon) <nodeCount×1.3。

[0136] Among them, if (pointCount-numPointCountRecon) is less than nodeCount×1.3, then planarEligibleK OctreeDepth is true; if (pointCount-numPointCountRecon) is not less than nodeCount×1.3, then planarEligibleKOctreeDepth is false. In this way, when planarEligibleKOctreeDepth is true, all nodes in the current layer are planar coded; otherwise, all nodes in the current layer are not planar coded and only octree coding is used.

[0137] 3. Determine whether the current node meets the plane coding requirements based on the acquisition parameters of the lidar point cloud.

[0138] Figure 9 shows a schematic diagram of the intersection of a laser radar and a node. As shown in Figure 9, a node filled with a grid is simultaneously traversed by two laser beams, so the current node is not a plane in the direction perpendicular to the Z axis. A node filled with a diagonal line is small enough to be traversed by two laser beams simultaneously, so it is possible that the node filled with a diagonal line is a plane in the direction perpendicular to the Z axis.

[0139] Furthermore, for nodes that meet the plane coding conditions, predictive coding may be performed on the plane identification information and the plane position information.

[0140] First, predictive coding of plane identification information.

[0141] Here, only three context information are used for encoding, that is, the plane identification in each coordinate dimension is designed separately for context.

[0142] Secondly, predictive coding of plane position information.

[0143] It should be understood that for the encoding of non-lidar point cloud planar position information, the predictive encoding of the planar position information may include:

[0144] (a) Using the occupancy information of neighboring nodes, the plane position information of the current node is predicted to be three elements: predicted as low plane, predicted as high plane, and unpredictable;

[0145] (b) Spatial distance between nodes at the same partition depth and coordinates as the current node and the current node: “near” and “far”;

[0146] (c) If the node at the same partition depth and the same coordinates as the current node is a plane, determine the plane position of the node;

[0147] (d) Coordinate dimension (i=0, 1, 2).

[0148] It should be noted that in an embodiment of the present application, after determining the spatial distance between the node at the same division depth and the same coordinates as the current node and the current node, if the spatial distance is less than the preset distance threshold, then the spatial distance can be determined to be "near"; or, if the spatial distance is greater than the preset distance threshold, then the spatial distance can be determined to be "far".

[0149] For example, Figure 10 shows a schematic diagram of neighboring nodes at the same partition depth and coordinates. As shown in Figure 10, the bold large cube represents the parent node, the small grid-filled cube inside it represents the current node, and the vertex position of the current node is shown. The small white-filled cube represents neighboring nodes at the same partition depth and coordinates. The distance between the current node and the neighboring node is the spatial distance, which can be judged as "near" or "far." In addition, if the neighboring node is a plane, the planar position of the neighboring node is also required.

[0150] In this way, as shown in Figure 10, the current node is a small cube filled with a grid, and the neighboring node is a small cube filled with white at the same octree partition depth level and the same vertical coordinate, and the distance between the two nodes is judged as "near" and "far", and the plane position of the reference node is used.

[0151] Furthermore, in an embodiment of the present application, FIG11 shows a schematic diagram of a current node being located at a low plane position of a parent node. As shown in FIG11 , (a), (b), and (c) show three examples of the current node being located at a low plane position of a parent node. Specific descriptions are as follows:

[0152] ① If any of the child nodes 4 to 7 of the point fill node is occupied, and all the grid fill nodes are not occupied, it is very likely that there is a plane in the current node (filled with a slash), and the plane is located lower.

[0153] ② If the child nodes 4 to 7 of the point fill node are not occupied, and any grid fill node is occupied, it is very likely that there is a plane in the current node (filled with diagonal lines), and the plane is located higher.

[0154] ③ If the child nodes 4 to 7 of the point fill node are all empty nodes and the grid fill nodes are all empty nodes, the plane position cannot be inferred and is therefore marked as unknown.

[0155] ④ If any of the child nodes 4 to 7 of the point fill node is occupied and any of the grid fill nodes is occupied, the plane position cannot be inferred at this time, so it is marked as unknown.

[0156] In an embodiment of the present application, FIG12 shows a schematic diagram of a current node being located at a high plane position of a parent node. As shown in FIG12, (a), (b), and (c) show three examples of the current node being located at a high plane position of a parent node. The specific description is as follows:

[0157] ① If any of the child nodes 4 to 7 of the grid fill node is occupied, and the point fill node is not occupied, it is very likely that there is a plane in the current node (filled with diagonal lines), and the plane position is low.

[0158] ② If the child nodes 4 to 7 of the grid fill node are not occupied, and the point fill node is occupied, it is very likely that there is a plane in the current node (filled with a slash), and the plane position is higher.

[0159] ③If the child nodes 4 to 7 of the grid fill node are all unoccupied, and the point fill node is unoccupied, the plane position cannot be inferred at this time, so it is marked as unknown.

[0160] ④ If one of the child nodes 4 to 7 of the grid fill node is occupied and the point fill node is occupied, the plane position cannot be inferred at this time and is therefore marked as unknown.

[0161] It should also be understood that, with respect to the coding of the laser radar point cloud plane position information, FIG13 shows a schematic diagram of the predictive coding of the laser radar point cloud plane position information. As shown in FIG13, when the laser radar emission angle is θ bottom When , it can be mapped to the bottom virtual plane; when the laser radar emission angle is θ top At this time, it can be mapped to the high plane (Top virtual plane).

[0162] That is, by using the laser radar acquisition parameters to predict the plane position of the current node, and by using the position where the current node intersects with the laser ray to quantize the position into multiple intervals, the final result is the context information of the plane position of the current node. The specific calculation process is as follows: Assume that the coordinates of the laser radar are (x Lidar ,y Lidar ,z Lidar ), the geometric coordinates of the current node are (x, y, z), then first calculate the vertical tangent value tan θ of the current node relative to the lidar, the calculation formula is as follows:

[0163] Furthermore, because each laser has a certain offset angle relative to the laser radar, it is also necessary to calculate the relative tangent value tan θ of the current node relative to the laser corr,L , the specific calculation is as follows:

[0164] Finally, the relative tangent value tan θ of the current node will be used corr,L To predict the plane position of the current node, as follows, assuming that the tangent value of the lower boundary of the current node is tan(θ bottom ), the tangent value of the upper boundary is tan(θ top ), according to tan θ corr,L The plane position is quantized into four quantization intervals, that is, the context information of the plane position is determined.

[0165] However, the octree-based geometric information coding mode only has an efficient compression rate for points that are correlated in space. For points that are isolated in the geometric space, the use of the Direct Coding Model (DCM) can greatly reduce the complexity. For all nodes in the octree, the use of DCM is not indicated by flag information, but is inferred from the parent node and neighbor information of the current node. There are three ways to determine whether the current node is eligible for DCM coding, as follows:

[0166] (1) The current node has no sibling child nodes, that is, the parent node of the current node has only one child node, and the parent node of the parent node of the current node has only two occupied child nodes, that is, the current node has at most one neighbor node.

[0167] (2) The parent node of the current node has only one child node, the current node, and the six neighbor nodes that share a face with the current node are all empty nodes.

[0168] (3) The number of sibling nodes of the current node is greater than 1.

[0169] Exemplarily, FIG14 provides a schematic diagram of IDCM coding. If the current node does not have the DCM coding qualification, it will be divided into octrees. If it has the DCM coding qualification, the number of points contained in the node will be further determined. When the number of points is less than a threshold (for example, 2), the node will be DCM-encoded, otherwise the octree division will continue. When the DCM coding mode is applied, it is first necessary to encode whether the current node is a true isolated point, that is, IDCM_flag. When IDCM_flag is true, the current node is DCM-encoded, otherwise octree coding is still used. When the current node meets the DCM coding requirements, the DCM coding mode of the current node needs to be encoded. There are currently two DCM modes: (a) there is only one point (or multiple points, but they are duplicate points); (b) there are two points. Finally, the geometric information of each point needs to be encoded. Assuming that the side length of the node is 2 d When encoding each component of the node's geometric coordinates, d bits are required, and these bits are directly encoded into the bitstream. It is important to note that when encoding LiDAR point clouds, the efficiency of geometric information coding can be further improved by predictively encoding the three-dimensional coordinate information using LiDAR acquisition parameters.

[0170] Furthermore, the IDCM encoding process is described in detail below.

[0171] When the current node meets the DCM encoding mode, the number of points of the current node, numPoints, is encoded first; the number of points of the current node is encoded according to different DirectModes:

[0172] ●If the current node does not meet the requirements of the DCM node, exit directly (that is, the number of points is greater than 2 points and it is not a duplicate point).

[0173] ●If the number of points numPonts in the current node is less than or equal to 2, the encoding process is as follows:

[0174] 1) First encode whether the numPonts of the current node is greater than 1;

[0175] 2) If the current node has only one point and the geometry coding environment is geometry lossless coding, it is necessary to encode the second point of the current node to ensure that it is not a duplicate point.

[0176] ●If the number of points numPonts in the current node is greater than 2, the encoding process is as follows:

[0177] 1) First encode the numPonts of the current node to be less than or equal to 1;

[0178] 2) Secondly, it is encoded that the second point of the current node is a repeated point, and then it is encoded whether the number of repeated points of the current node is greater than 1. When the number of repeated points is greater than 1, the remaining number of repeated points needs to be exponentially decoded.

[0179] After encoding the number of points in the current node, the coordinate information of the points contained in the current node is encoded. The following will introduce the lidar point cloud and the human eye point cloud in detail.

[0180] (1) Point cloud facing the human eye.

[0181] (1) If the current node contains only one point, the geometric information of the point in three dimensions will be directly encoded (Bypass coding);

[0182] (2) If the current node contains two points, the first coordinate axis dirextAxis will be obtained by using the geometric coordinates of the points. It should be noted that the coordinate axes currently compared only include the x-axis and y-axis, not the z-axis. Assuming that the geometric coordinates of the current node are nodePos, the judgment method is as follows: dirextAxis = !(nodePos[0]<nodePos[1])

[0183] That is, the axis with the smallest node coordinate geometry position will be used as the priority encoding axis dirextAxis, and then the geometry information of the priority encoding axis dirextAxis will be encoded as follows. Assume that the encoding geometry bit depth corresponding to the priority encoding axis is nodeSizeLog2, and assume that the coordinates of the two points are pointPos[0] and pointPos[1]. The specific encoding process is as follows:

[0184] After encoding the priority axis dirextAxis, continue to directly encode the geometric coordinates of the current node. Assuming that the remaining encoding bit depth of each point is nodeSizeLog2, the specific encoding process is as follows: for(int axisIdx=0;axisIdx<3;++axisIdx) for(int mask=(1<<nodeSizeLog2[axisIdx])> >1;mask;mask>>1) encodePosBit(!!(pointPos[axisIdx]&mask)).

[0185] (2) LiDAR point cloud.

[0186] If the current node contains two points, the priority coded coordinate axis dirextAxis will be obtained first by using the geometric coordinates of the points. Assuming that the geometric coordinates of the current node are nodePos, the judgment method is as follows: dirextAxis = !(nodePos[0]<nodePos[1])

[0187] That is, the axis with the smaller node coordinate geometry position will be used as the priority encoding axis dirextAxis. It should be noted that the currently compared coordinate axes only include the x-axis and y-axis, not the z-axis. Then, the geometric information of the priority encoded coordinate axis dirextAxis is first encoded as follows, assuming that the encoding geometry bit depth corresponding to the priority encoded axis is nodeSizeLog2, and assuming that the coordinates of the two points are pointPos[0] and pointPos[1]. The specific encoding process is as follows:

[0188] After encoding the priority-encoded coordinate axis dirextAxis, the geometric coordinates of the current node are encoded.

[0189] Since the LiDAR point cloud can obtain the acquisition parameters of the LiDAR point cloud, the geometric coordinate information of the current node can be predicted, thereby further improving the efficiency of the geometric information encoding of the point cloud. Similarly, the geometric information nodePos of the current node is first used to obtain a directly encoded main axis direction, and then the geometric information of the encoded direction is used to predict the geometric information of another dimension. Also assuming that the axis direction of the direct encoding is directAxis, and assuming that the bit depth of the direct encoding is nodeSizeLog2, the encoding method is as follows: for(int mask=(1<<nodeSizeLog2)> >1;mask;mask>>1) encodePosBit(!!(pointPos[directAxis]&mask)).

[0190] It should be noted here that all geometric accuracy information in the directAxis direction will be encoded here.

[0191] For example, Figure 15 provides a schematic diagram of coordinate transformation for obtaining point clouds using a rotating laser radar. In the Cartesian coordinate system, the (x, y, z) coordinates of each node can be converted to Indicates. In addition, the laser scanner can perform laser scanning at a preset angle, and different θ(i) can be obtained under different values ​​of i. For example, when i is equal to 1, θ(1) can be obtained, and the corresponding scanning angle is -15°; when i is equal to 2, θ(2) can be obtained, and the corresponding scanning angle is -13°; when i is equal to 10, θ(10) can be obtained, and the corresponding scanning angle is +13°; when i is equal to 9, θ(19) can be obtained, and the corresponding scanning angle is +15°.

[0192] In this way, after encoding all the precision of the directAxis coordinate direction, the LaserIdx corresponding to the current point will be calculated first, that is, the pointLaserIdx number in Figure 15, and the LaserIdx of the current node, that is, nodeLaserIdx; secondly, the LaserIdx of the node, that is, nodeLaserIdx, will be used to predict the LaserIdx of the point, that is, pointLaserIdx. The calculation method of the LaserIdx of the node or point is as follows. Assuming that the geometric coordinates of the point are pointPos, the starting coordinates of the laser ray are LidarOrigin, and assuming that the number of Lasers is LaserNum, the tangent value of each Laser is tanθ i , the vertical offset position of each Laser is Z i ,but:

[0193] After calculating the current point's LaserIdx, the LaserIdx of the current node is first used to predictively encode the pointLaserIdx. After encoding the current point's LaserIdx, the three-dimensional geometric information of the current point is predictively encoded using the LiDAR acquisition parameters.

[0194] For example, FIG16 shows a schematic diagram of predictive coding in the X-axis or Y-axis direction. As shown in FIG16 , the box filled with a grid represents the current node, and the box filled with a slash represents the already coded node. Here, the LaserIdx corresponding to the current point is first used to obtain the corresponding predicted value of the horizontal azimuth, that is, Secondly, the node geometry information corresponding to the current point is used to obtain the horizontal azimuth angle corresponding to the node Assuming that the geometric coordinates of the node are nodePos, the horizontal azimuth angle is The calculation method between the node geometry information is as follows:

[0195] By using the acquisition parameters of the laser radar, we can get the number of rotation points of each laser, numPoints, which represents the number of points obtained by each laser ray rotating one circle. Then, we can use the number of rotation points of each laser to calculate the rotation angular velocity deltaPhi of each laser. The calculation method is as follows:

[0196] Furthermore, using the horizontal azimuth angle of the node And the horizontal azimuth of the previous Laser code point corresponding to the current point Calculate the predicted horizontal azimuth angle corresponding to the current point That is, the predicted value of the horizontal azimuth angle as shown in Figure 17A and Figure 17B. Figure 17A shows a schematic diagram of predicting the angle of the Y plane through the horizontal azimuth angle, and Figure 17B shows a schematic diagram of predicting the angle of the X plane through the horizontal azimuth angle. Here, the predicted value of the horizontal azimuth angle corresponding to the current point is The calculation is as follows:

[0197] For example, FIG18 shows another schematic diagram of predictive coding in the X-axis or Y-axis direction. As shown in FIG18 , the portion filled with a grid (left side) represents a low plane, and the portion filled with dots (right side) represents a high plane. Indicates the low plane horizontal azimuth of the current node, Indicates the horizontal azimuth of the current node’s high plane. Indicates the predicted horizontal azimuth angle corresponding to the current node.

[0198] Thus, by using the predicted value of the horizontal azimuth and the low plane horizontal azimuth of the current node and the high plane horizontal azimuth To predict the geometric information of the current node. The details are as follows: int context=(angLel≥0&&angLeR≥0)||(angLel<0&&angLeR<0)? 0:2; int minAngle=std∷min(abs(angLel),abs(angLeR)); int maxAngle=std∷max(abs(angLel),abs(angLeR)); context+=maxAngle>minAngle? 0:1; context+=maxAngle>minAngle? 0:4.

[0199] After encoding the LaserIdx of the point, the Z-axis direction of the current point will be predicted using the LaserIdx corresponding to the current point. That is, the depth information radius of the radar coordinate system is calculated by using the x and y information of the current point. Then, the tangent value of the current point and the vertical offset are obtained using the LaserIdx of the current point. The predicted value of the Z-axis direction of the current point, namely Z_pred, can be obtained. The details are as follows: int tanTheta=tanθ laserIdx ; int zOffset = Z laserIdx ; Z_pred=radius×tanTheta-zOffset.

[0200] Furthermore, Z_pred is used to perform predictive coding on the geometric information of the current point in the Z-axis direction to obtain the prediction residual Z_res, and finally Z_res is encoded.

[0201] It is important to note that when partitioning nodes into leaf nodes, the number of duplicate points in the leaf nodes must be encoded in the case of lossless geometric coding. Ultimately, the placeholder information for all nodes is encoded to generate a binary bitstream. Furthermore, G-PCC currently introduces a plane coding mode. During the geometric partitioning process, it determines whether the child nodes of the current node are in the same plane. If the child nodes of the current node meet the condition of being in the same plane, the child nodes of the current node are represented by that plane.

[0202] For octree-based geometric decoding, the decoder follows a breadth-first traversal. Before decoding each node's occupancy information, it first uses the reconstructed geometric information to determine whether the current node is for plane decoding or IDCM decoding. If the current node meets the requirements for plane decoding, it first decodes the plane identifier and plane position information of the current node. Then, based on the plane information, it decodes the current node's occupancy information. If the current node meets the requirements for IDCM decoding, it first decodes whether the current node is a true IDCM node. If so, it continues to parse the DCM decoding mode of the current node, then obtains the number of points in the current DCM node, and finally decodes the geometric information of each point. For nodes that do not meet either plane decoding or DCM decoding requirements, the current node's occupancy information is decoded. By continuously parsing in this way, the placeholder code of each node is obtained, and the node is continuously partitioned until a 1×1×1 unit cube is obtained. The number of points contained in each leaf node is parsed, and the geometrically reconstructed point cloud information is finally recovered.

[0203] The following is a detailed introduction to the IDCM decoding process.

[0204] Similar to the processing at the encoding end, we first use prior information to determine whether the node should start IDCM. The starting conditions of IDCM are as follows:

[0205] (1) The current node has no sibling child nodes, that is, the parent node of the current node has only one child node, and the parent node of the parent node of the current node has only two occupied child nodes, that is, the current node has at most one neighbor node.

[0206] (2) The parent node of the current node has only one child node, the current node, and the six neighbor nodes that share a face with the current node are all empty nodes.

[0207] (3) The number of sibling nodes of the current node is greater than 1.

[0208] Furthermore, when a node meets the conditions for DCM coding, it is first decoded to determine whether the current node is a true DCM node, that is, IDCM_flag; when IDCM_flag is true, the current node adopts DCM coding, otherwise it still adopts octree coding.

[0209] Next, decode the number of points numPoints of the current node. The specific decoding method is as follows:

[0210] i) First decode whether numPonts of the current node is greater than 1;

[0211] ii) If the numPonts of the current node is greater than 1, continue decoding to see if the second point is a duplicate point; if the second point is not a duplicate point, it can be implicitly inferred that the second type of DCM mode contains only two points;

[0212] iii) If the numPonts of the current node obtained by decoding is less than or equal to 1, continue decoding to see if the second point is a repeated point; if the second point is not a repeated point, it can be implicitly inferred that the second type of DCM pattern is satisfied, which contains only one point; if the second point obtained by decoding is a repeated point, it can be inferred that the third type of DCM pattern is satisfied, which contains multiple points, but they are all repeated points, then continue decoding to see if the number of repeated points is greater than 1 (entropy decoding), and if it is greater than 1, continue decoding the number of remaining repeated points (using exponential Columbus decoding).

[0213] If the current node does not meet the requirements of the DCM node, it will exit directly (that is, the number of points is greater than 2 points and it is not a duplicate point).

[0214] After decoding the number of points in the current node, the coordinate information of the points contained in the current node is decoded. The following will introduce the lidar point cloud and the human eye point cloud in detail.

[0215] (1) Point cloud facing the human eye.

[0216] (1) If the current node contains only one point, the geometric information of the point in three dimensions will be directly decoded (Bypass coding);

[0217] (2) If the current node contains two points, the first coordinate axis to be decoded is obtained by using the geometric coordinates of the points. It should be noted that the coordinate axes currently compared only include the x and y axes, not the z axis. Assuming that the geometric coordinates of the current node are nodePos, the judgment method is as follows: dirextAxis = (nodePos[0] < nodePos[1])

[0218] That is, the axis with the smallest node coordinate geometry position will be used as the priority decoding axis dirextAxis, and then the geometry information of the priority decoding axis dirextAxis will be decoded first in the following way. Assume that the geometry bit depth to be decoded corresponding to the priority decoding axis is nodeSizeLog2, and assume that the coordinates of the two points are pointPos[0] and pointPos[1]. The specific encoding process is as follows:

[0219] After decoding the prioritized axis dirextAxis, the geometric coordinates of the current point are directly decoded. Assuming the remaining encoding bit depth of each point is nodeSizeLog2 and the coordinate information of the point is pointPos, the specific decoding process is as follows:

[0220] (2) LiDAR point cloud.

[0221] If the current node contains two points, the priority decoding coordinate axis dirextAxis will be obtained first by using the geometric coordinates of the points. Assuming that the geometric coordinates of the current node are nodePos, the judgment method is as follows: dirextAxis = ! (nodePos[0] < nodePos[1]) (11)

[0222] That is, the axis with the smaller node coordinate geometry position will be used as the priority decoding axis dirextAxis. It should be noted that the currently compared coordinate axes only include the x-axis and y-axis, not the z-axis. Secondly, the priority encoded coordinate axis dirextAxis geometry information is first decoded as follows, assuming that the encoding geometry bit depth corresponding to the priority decoded axis is nodeSizeLog2, and assuming that the coordinates of the two points are pointPos[0] and pointPos[1]. The specific encoding process is as follows:

[0223] After decoding the priority coordinate axis dirextAxis, the geometric coordinates of the current point are decoded.

[0224] Similarly, we first use the current node's geometry information nodePos to get a direct decoding main axis direction, and then use the geometry information of the decoded direction to decode the geometry information of the other dimension. Assuming that the axis direction of direct decoding is directAxis and the bit depth to be decoded in direct decoding is nodeSizeLog2, the decoding method is as follows:

[0225] It should be noted here that all geometric accuracy information in the directAxis direction will be decoded here.

[0226] After decoding all the accuracies of the directAxis coordinate direction, the LaserIdx of the current node, i.e., nodeLaserIdx, is calculated first. Secondly, the LaserIdx of the node, i.e., nodeLaserIdx, is used to predict and decode the LaserIdx of the point, i.e., pointLaserIdx. The calculation method of the LaserIdx of the node or point is the same as that of the encoding end. Finally, the predicted residual information of the LaserIdx of the current point and the LaserIdx of the node is decoded to obtain ResLaserIdx. The decoding method is as follows: PointLaserIdx = nodeLaserIdx + ResLaserIdx

[0227] After decoding the LaserIdx of the current point, the three-dimensional geometric information of the current point is predicted and decoded using the acquisition parameters of the laser radar. The specific algorithm is as follows:

[0228] As shown in Figure 11, the LaserIdx corresponding to the current point is first used to obtain the corresponding predicted value of the horizontal azimuth angle, that is, Secondly, the node geometry information corresponding to the current point is used to obtain the horizontal azimuth angle corresponding to the node Assuming that the geometric coordinates of the node are nodePos, the horizontal azimuth angle is The calculation method between the node geometry information is as follows:

[0229] By using the acquisition parameters of the laser radar, we can get the number of rotation points of each laser, numPoints, which represents the number of points obtained by each laser ray rotating one circle. Then, we can use the number of rotation points of each laser to calculate the rotation angular velocity deltaPhi of each laser. The calculation method is as follows:

[0230] Furthermore, using the horizontal azimuth angle of the node And the horizontal azimuth of the previous Laser code point corresponding to the current point Calculate the predicted horizontal azimuth angle corresponding to the current point That is, the predicted value of the horizontal azimuth angle as shown in Figures 17A and 17B. The calculation method is as follows:

[0231] Thus, by using the predicted value of the horizontal azimuth and the low plane horizontal azimuth of the current node and the horizontal azimuth of the high plane To predict and decode the geometric information of the current node. The details are as follows: int context=(angLel≥0&&angLeR≥0)||(angLel<0&&angLeR<0)? 0:2; int absAngleL=abs(angLel); int absAngleR=abs(angLeR); context+=absAngleL>absAngleR? 0:1; context+=maxAngle>minAngle<<1? 4:0.

[0232] After decoding the LaserIdx of the completed point, the Z-axis direction of the current point will be predicted and decoded using the LaserIdx corresponding to the current point. That is, the depth information radius of the radar coordinate system is calculated by using the x and y information of the current point. Then, the tangent value of the current point and the vertical offset are obtained using the LaserIdx of the current point. The predicted value of the Z-axis direction of the current point, namely Z_pred, can be obtained. The details are as follows: int tanTheta=tanθ laserIdx ; int zOffset = Z laserIdx; Z_pred=radius×tanTheta-zOffset.

[0233] Furthermore, the decoded Z_res and Z_pred are used to reconstruct and restore the geometric information of the current point in the Z-axis direction.

[0234] For triangle soup (trisoup)-based geometric information coding, geometric partitioning must also be performed first in the trisoup-based geometric information coding framework. However, unlike geometric information coding based on binary trees, quadtrees, and octrees, this method does not require step-by-step partitioning of the point cloud into unit cubes with side lengths of 1×1×1. Instead, the partitioning stops when the sub-blocks (blocks) have a side length of W. Based on the surface formed by the distribution of the point cloud in each block, the surface and the twelve edges of the block are obtained. The vertex coordinates of each block are encoded in sequence to generate a binary code stream.

[0235] For trisoup-based point cloud geometry reconstruction, when performing point cloud geometry reconstruction at the decoding end, the vertex coordinates are first decoded to complete the triangle face reconstruction. This process is shown in Figures 19A, 19B, and 19C. Among them, there are three intersection points (v1, v2, v3) in the block shown in Figure 19A. The set of triangle faces formed by these three intersection points in a certain order is called triangle soup, or trisoup, as shown in Figure 19B. Afterwards, sampling is performed on the triangle face set, and the obtained sampling points are used as the reconstructed point cloud within the block, as shown in Figure 19C.

[0236] For predictive geometry coding (PredGeomTree), the following steps are involved: first, sort the input point cloud. Currently, the sorting methods used include unordered, Morton order, azimuth order, and radial distance order. At the encoding end, the prediction tree structure is established using two different methods: KD-Tree (high-latency slow mode) and low-latency fast mode (using lidar calibration information). When using lidar calibration information, each point is divided into different lasers, and a prediction tree structure is established according to the different lasers. Next, based on the structure of the prediction tree, each node in the prediction tree is traversed, and the geometric position information of the node is predicted by selecting different prediction modes to obtain the prediction residual, and the geometric prediction residual is quantized using the quantization parameter. Finally, through continuous iteration, the prediction residual of the prediction tree node position information, the prediction tree structure, and the quantization parameter are encoded to generate a binary code stream.

[0237] For geometric decoding based on the prediction tree, the decoding end reconstructs the prediction tree structure by continuously parsing the bit stream. Secondly, the geometric position prediction residual information and quantization parameters of each prediction node are obtained through parsing, and the prediction residual is dequantized to restore the reconstructed geometric position information of each node, finally completing the geometric reconstruction at the decoding end.

[0238] After the geometric encoding is completed, the geometric information needs to be reconstructed. At present, attribute encoding is mainly performed on color information. First, the color information is converted from the RGB color space to the YUV color space. Then, the point cloud is recolored using the reconstructed geometric information so that the unencoded attribute information corresponds to the reconstructed geometric information. In color information encoding, there are two main transformation methods. One is the distance-based lifting transformation that relies on LOD partitioning, and the other is to directly perform RAHT transformation. Both methods will convert the color information from the spatial domain to the frequency domain, and obtain high-frequency coefficients and low-frequency coefficients through transformation. Finally, the coefficients are quantized and encoded to generate a binary code stream, as shown in Figures 4A and 4B.

[0239] Furthermore, when using geometric information to predict attribute information, Morton codes can be used to perform nearest neighbor search. The Morton code corresponding to each point in the point cloud can be obtained from the geometric coordinates of the point. The specific method for calculating the Morton code is described below. For a three-dimensional coordinate represented by a d-bit binary number for each component, its three components can be expressed as:

[0240] in, The highest bits of x, y, and z respectively To the lowest position The corresponding binary value. The Morton code M is x, y, z starting from the highest bit, arranged in sequence To the lowest bit, the calculation formula of M is as follows:

[0241] in, The highest bit of M To the lowest position After obtaining the Morton code M of each point in the point cloud, the points in the point cloud are arranged in ascending order of the Morton code, and the weight value w of each point is set to 1.

[0242] It can also be understood that for the G-PCC codec framework, the general test conditions are as follows:

[0243] (1) There are 4 test conditions:

[0244] Condition 1: The geometric position is limited and the attributes are lost;

[0245] Condition 2: Geometric position lossless, attribute lossy;

[0246] Condition 3: Geometric position lossless, attribute loss limited;

[0247] Condition 4: Geometric position and attributes are lossless.

[0248] (2) The general test sequence includes four categories: Cat1A, Cat1B, Cat3-fused, and Cat3-frame. Among them, Cat2-frame point cloud only contains reflectance attribute information, Cat1A and Cat1B point clouds only contain color attribute information, and Cat3-fused point cloud contains both color and reflectance attribute information.

[0249] (3) Technical routes: There are two types in total, which are distinguished by the algorithm used for geometric compression.

[0250] Technical route 1: Octree encoding branch.

[0251] At the encoding end, the bounding box is divided into sub-cubes in sequence, and the non-empty sub-cubes (containing points in the point cloud) are divided again until the leaf node obtained is a 1×1×1 unit cube. In the case of geometric lossless coding, the number of points contained in the leaf node needs to be encoded, and finally the geometric octree encoding is completed to generate a binary code stream.

[0252] At the decoding end, the decoding end obtains the placeholder code of each node by continuously parsing in the order of breadth-first traversal, and continuously divides the nodes in turn until a 1×1×1 unit cube is obtained. In the case of geometric lossless decoding, it is necessary to parse the number of points contained in each leaf node and finally recover the geometrically reconstructed point cloud information.

[0253] Technical route 2: prediction tree encoding branch.

[0254] On the encoding side, the prediction tree structure is established using two different methods: based on KD-Tree (high-latency slow mode) and using lidar calibration information (low-latency fast mode). Using lidar calibration information, each point can be divided into different lasers, and the prediction tree structure is established according to different lasers. Next, based on the structure of the prediction tree, each node in the prediction tree is traversed, and the geometric position information of the node is predicted by selecting different prediction modes to obtain the prediction residual, and the geometric prediction residual is quantized using the quantization parameter. Finally, through continuous iteration, the prediction residual of the prediction tree node position information, the prediction tree structure, and the quantization parameters are encoded to generate a binary code stream.

[0255] At the decoding end, the decoding end continuously analyzes the bitstream to reconstruct the prediction tree structure. Secondly, it obtains the geometric position prediction residual information and quantization parameters of each prediction node through analysis, and inverse-quantizes the prediction residuals to restore the reconstructed geometric position information of each node, finally completing the geometric reconstruction at the decoding end.

[0256] It should also be noted that as shown in FIG. 4A or FIG. 4B, the current G-PCC coding framework includes three attribute coding methods: Predicting Transform (PT), Lifting Transform (LT), and Region Adaptive Hierarchical Transform (RAHT). Among them, the first two perform point cloud prediction coding based on the generation order of LODs, while RAHT adaptively transforms the attribute information from bottom to top according to the construction levels of the octree. The following will introduce these three point cloud attribute coding methods in detail.

[0257] (a) Predictive coding of point cloud attribute information.

[0258] Currently, the attribute prediction module of G-PCC adopts a nearest neighbor attribute prediction coding scheme based on a Level-of-details (LoDs) structure. The construction methods of LODs include a distance-based LOD construction scheme, a fixed sampling rate-based LOD construction scheme, and an octree-based LOD construction scheme, etc. In the distance threshold-based LOD construction scheme, before constructing the LOD, the point cloud is first sorted by Morton to ensure strong attribute correlation between adjacent points. FIG. 20 is a schematic diagram of a distance-based LOD construction process. As shown in FIG. 20, according to L Manhattan distances (dl) preset by the user in advance, l = 0, 1, … L-1; the point cloud is divided into L different point cloud detail levels (Rl), l = 0, ½ L-1, where (dl)l = 0, 1, … L-1 satisfies dl < dl-1. The LOD construction process is as follows:

[0259] (1) First, mark all points in the point cloud as unvisited, and establish a set V to store the set of visited points; (2) For each iteration l, traverse the points in the point cloud. If the current point has been visited, ignore it; otherwise, calculate the minimum distance D from the current point to the set V. If D < dl, ignore the point; otherwise, mark the current point as visited and add the current point to the refinement level Rl and the set V; (3) The points in the detail level LODl are composed of the points in the refinement levels R0, R1, R2…Rl; (4) Continuously repeat the above steps until all points are marked as visited.

[0260] Based on the LOD structure, the attribute value of each point is linearly weighted predicted using the attribute reconstruction values ​​of points in the same or higher LOD layer. The maximum number of reference prediction neighbors is determined by the encoder's high-level syntax elements. For each point attribute, the encoder uses a rate-distortion optimization algorithm to select a weighted prediction using the attributes of the N nearest neighbors found, or a single nearest neighbor for prediction. Finally, the selected prediction mode and prediction residual are encoded.

[0261] Among them, N represents the number of predicted points in the nearest neighbor point set of point i, Pi represents the sum of the N nearest neighbor points of point i, Dm represents the spatial geometric distance from the nearest neighbor point m to the current point i, Attrm represents the attribute value of the nearest neighbor point m after reconstruction, Attr i ′ represents the attribute prediction value of the current point i, and the number of points N is a preset value.

[0262] To balance attribute coding efficiency and parallel processing between different LOD layers, a switch is introduced in the encoder's high-level syntax elements to control whether to use intra-LOD prediction. If turned on, intra-LOD prediction is enabled, allowing predictions to be made using points within the same LOD layer. Note that when the number of LOD layers is 1, intra-LOD prediction is always used.

[0263] Figure 21 shows a visualization of the LOD generation process. This provides a subjective example of the distance-based LOD generation process. Specifically (from left to right): points in the first layer represent the outer contours of the point cloud; as the number of detail layers increases, the point cloud details become increasingly clear.

[0264] Figure 22 is a schematic diagram of the attribute prediction encoding process. As shown in Figure 22, for the specific process of G-PCC attribute prediction, for the original point cloud, the three nearest neighbors of the Kth point are first searched, and then attribute prediction is performed. The difference between the attribute prediction value of the Kth point and the original attribute value of the Kth point is calculated to obtain the prediction residual of the Kth point. Quantization and arithmetic coding are then performed to finally generate the attribute bit rate.

[0265] (i) Optimal prediction value selection:

[0266] After the LOD is constructed, according to the generation order of LOD, the three nearest neighboring points of the current point to be encoded are first found from the encoded data points. The attribute reconstruction values ​​of these three nearest neighboring points are used as candidate prediction values ​​of the current point to be encoded; then, the optimal prediction value is selected from them according to the rate-distortion optimization (RDO). For example, when encoding the attribute value of point P2 in Figure 20, the prediction variable index of the attribute value of the nearest neighbor point P4 is set to 1; the attribute prediction variable indexes of the second nearest neighbor point P5 and the third nearest neighbor point P0 are set to 2 and 3 respectively; the prediction variable index of the weighted average of points P0, P5 and P4 is set to 0, as shown in Table 1; finally, RDO is used to select the best prediction variable. The formula for weighted average is as follows:

[0267] in, Represents the spatial geometric weight of the neighboring point j to the current point i:

[0268] Represents the attribute prediction value of the current point i, j represents the index of the three neighboring points, Represents the attribute value after reconstruction of the neighboring points, x i ,y i ,z i is the geometric position coordinate of the current point i, x ij ,y ij ,z ij is the geometric coordinate of the neighboring point j.

[0269] For example, Table 1 provides an example of candidate prediction item samples for an attribute code.

[0270] Table 1

[0271] (ii) Attribute prediction residuals and quantification:

[0272] The attribute prediction value of the current point i is obtained through the above prediction (k is the total number of points in the point cloud). Let (a i ) i∈0…k-1 is the original value of the attribute of the current point, then the attribute residual (r i ) i∈0…k-1 Denoted as:

[0273] Further quantify the prediction residuals:

[0274] Among them, Q iIt represents the quantized attribute residual of the current point i, Qs is the quantization step (Qs), which can be calculated by the quantization parameter QP (QP) specified by CTC.

[0275] (iii) The encoding end reconstructs the attribute value:

[0276] The purpose of reconstruction at the encoding end is to predict the subsequent points. Before reconstructing the attribute value, the residual must be dequantized. is the residual after inverse quantization:

[0277] and predicted value Add up to get the reconstruction value of point i

[0278] There are currently two main types of algorithms for attribute nearest neighbor search based on LOD partitioning: intra-frame nearest neighbor search and inter-frame nearest neighbor search. The inter-frame nearest neighbor search algorithm is detailed below, while the intra-frame nearest neighbor search can be divided into inter-layer nearest neighbor search and intra-layer nearest neighbor search.

[0279] (i) Intra-frame nearest neighbor search:

[0280] Intra-frame nearest neighbor search is divided into two algorithms: inter-layer nearest neighbor search and intra-layer nearest neighbor search. After LOD division, it resembles a pyramid structure, as shown in Figure 23.

[0281] In a specific implementation, for inter-layer nearest neighbor search, the pyramid structure is shown in FIG24. FIG25 is a pyramid structure for inter-layer nearest neighbor search.

[0282] Schematic diagram of the LOD construction process of neighbor search. As shown in Figure 25, different LOD layers are obtained based on geometric information division.

[0283] LOD0, LOD1 and LOD2 use the points in LOD0 to predict the attributes of the points in the next layer of LOD in the nearest neighbor search between layers

[0284] In the process.

[0285] The entire process of searching for the nearest neighbor within a frame is described in detail below.

[0286] During the entire LOD partitioning process, there are three sets: O(k), L(k), and I(k). Among them, k is the index of the LOD layer during LOD partitioning, and I(k) is the input point set during the current LOD layer partitioning. After LOD partitioning, the O(k) set and L(k) set are obtained. The O(k) set stores the sampling point set, and L(k) is the point set in the current LOD layer. The entire LOD partitioning process is as follows:

[0287] (1) Initialization.

[0288] if k=0,L(k)←{}; otherwise,L(k)←L(k-1);

[0289] O(k)←{};

[0290] (2) Using the LOD partitioning algorithm, the sampling points are stored in O(k), and the remaining points are divided into L(k);

[0291] (3) When the next iteration is performed, I←O(k).

[0292] It should be noted here that since the entire LOD division process is based on the Morton code, O(k), L(k) and I(k) store the Morton code index corresponding to the point.

[0293] When performing inter-layer nearest neighbor search, that is, the points in the L(k) set perform nearest neighbor search in the O(k) set. The specific search algorithm is as follows:

[0294] Taking the nearest neighbor search based on spatial relationships as an example, when predicting the current point P, the neighbor search is performed by using the parent block (Block B) corresponding to point P. As shown in Figure 26, points in the neighbor blocks that are coplanar or colinear with the current parent block are searched for attributes.

[0295] Figure 27A shows a schematic diagram of a coplanar spatial relationship, where there are 6 spatial blocks that have a relationship with the current parent block. Figure 27B shows a schematic diagram of a coplanar and colinear spatial relationship, where there are 18 spatial blocks that have a relationship with the current parent block. Figure 27C shows a schematic diagram of a coplanar, colinear, and co-point spatial relationship, where there are 26 spatial blocks that have a relationship with the current parent block.

[0296] First, the coordinates of the current point are used to obtain the corresponding spatial block. Second, a nearest neighbor search is performed in the previously encoded LOD layer to find the spatial blocks that are coplanar, colinear, and co-point with the current block to obtain the N nearest neighbors of the current point.

[0297] After performing coplanar, colinear, and co-point nearest neighbor searches, if the N nearest neighbors of the current point are still not found, the N nearest neighbors of the current point will be found based on a fast search algorithm. The specific algorithm is as follows:

[0298] As shown in Figure 28, when performing inter-attribute layer prediction, the geometric coordinates of the current point to be encoded are first used to obtain the Morton code corresponding to the current point. Secondly, based on the Morton code of the current point, the first reference point (j) with a value greater than the Morton code of the current point is found in the reference frame. Then, the nearest neighbor search is performed within the range of [j-searchRange, j+searchRange].

[0299] The rest of the specific algorithms for updating the nearest neighbor are the same as the inter-frame nearest neighbor search algorithm and will not be described in detail here. The specific algorithms will be mentioned in the inter-frame nearest neighbor search algorithm.

[0300] In another specific implementation, for the nearest neighbor search within a layer, Figure 29 shows a schematic diagram of the LOD structure of the nearest neighbor search within an attribute layer. As shown in Figure 29, if the intra-layer prediction algorithm is turned on, that is, the syntax element EnableRefferingSameLoD=1, then the nearest neighbor search within the layer can be allowed. For example, for the LOD1 layer, the nearest neighbor point of the current point P6 can be P1, which is not allowed in other layers; if the syntax element EnableRefferingSameLoD=0, then inter-layer search is allowed in other layers. For example, for the LOD1 layer, the nearest neighbor point of the current point P6 can be P4. That is to say, when the intra-layer prediction algorithm is turned on, the nearest neighbor search will be performed in the same layer LOD and the set of encoded points in the same layer to obtain the N nearest neighbors of the current point (the inter-layer nearest neighbor search is also performed).

[0301] When performing prediction within the attribute layer, a nearest neighbor search is performed based on a fast search algorithm. The specific algorithm is shown in Figure 30. The current point is represented by a grid. Assuming the Morton code index of the current point is i, the nearest neighbor search is performed in [i+1, i+searchRange]. The specific nearest neighbor search algorithm is consistent with the inter-frame block-based fast search algorithm and is not described in detail here.

[0302] (ii) Nearest neighbor search between frames:

[0303] Figure 28 is a schematic diagram of attribute inter-frame prediction. As shown in Figure 28, when performing attribute inter-frame prediction, the geometric coordinates of the current point to be encoded are first used to obtain the Morton code corresponding to the current point. Then, based on the Morton code of the current point, the first reference point (j) with a Morton code greater than the current point is found in the reference frame. Then, the nearest neighbor search is performed within the range [j-searchRange, j+searchRange].

[0304] The current nearest neighbor search within and between frames is based on block-based neighborhood search, as shown in Figure 31. As shown in Figure 31, when performing neighborhood search for the current point (Morton code index is i), the points in the reference frame are first divided into N (N=3) layers according to the Morton code. The specific division algorithm is as follows:

[0305] First layer: Assume that the points of the reference frame are numPoints, first divide the points in the reference frame into M (M=2 5 =32) points are divided into one block;

[0306] Second layer: Based on the first layer, the blocks of the first layer are also processed in the order of Morton code every M (M=2 5 =32) blocks are divided into one block;

[0307] The third layer: Based on the second layer, the blocks of the second layer are also processed in the order of the Morton code every M (M=2 5 =32) blocks are divided into one block;

[0308] Finally, the predicted structure shown in Figure 31 is obtained.

[0309] When performing attribute prediction based on the prediction structure shown in Figure 31, assuming that the Morton code index of the current point to be encoded is i, first obtain the first point in the reference frame whose Morton code is greater than or equal to the current point, with index j. Then, the block index of the reference point is calculated based on j. The specific calculation method is as follows:

[0310] First layer: BucketSize_0 = 2 5 =32;

[0311] Second layer: BucketSize_1 = 2 5 =32×BucketSize_0=1024;

[0312] Third layer: BucketSize_2 = 2 5 =32×BucketSize_1=32768.

[0313] Assume that the reference range in the prediction frame of the current point is [j-searchRange, j+searchRange], use j-searchRange to calculate the starting index of the third layer, and use j+searchRange to calculate the ending index of the third layer; secondly, first determine whether some blocks in the second layer need to be searched for the nearest neighbor in the blocks of the third layer, and then go to the second layer, and determine whether a search is needed for each block in the first layer. If some blocks in the first layer need to be searched for the nearest neighbor, then the midpoints of some blocks in the first layer will be judged point by point to update the nearest neighbor.

[0314] The following is an introduction to the algorithm based on index calculation block. Assuming that the Morton code index corresponding to the current point is index, then the index of the corresponding third-level block is: idx_2 = index / BucketSize_2

[0315] After obtaining the block index idx_2 of the third layer, the start index and end index of the block corresponding to the current block in the second layer can be obtained using idx_2: startIdx1=idx_2×BucketSize_1 endIdx=idx_2×BucketSize_1+BucketSize_1-1

[0316] Similarly, the index of the first layer block is obtained based on the index of the second layer block based on the same algorithm.

[0317] When performing a block-based nearest neighbor search, we first determine whether the current block needs to be searched for the nearest neighbor. This is called filtering the nearest neighbor search for the block. Each spatial block can be obtained through two variables: minPos and maxPos. MinPos represents the minimum value of the block, and maxPos represents the maximum value of the block.

[0318] Assume that the distance to the farthest point among the N nearest neighbors of the current point is Dist, the coordinates of the point to be encoded are (x, y, z), and the current block is represented by (minPos, maxPos), where minPos is the minimum value of the three dimensions of the bounding box and maxPos is the maximum value of the three dimensions of the bounding box. The distance D between the current point and the bounding box is calculated as follows: int dx = int(std::max(std::max(minPos[0]-point[0],0),point[0]-maxPos[0])); int dy = int(std::max(std::max(minPos[1]-point[1],0),point[1]-maxPos[1])); int dz = int(std::max(std::max(minPos[2]-point[2],0),point[2]-maxPos[2])); D = dx+dy+dz;

[0319] When D is less than or equal to Dist, the points in the current block will be traversed.

[0320] (b) Lifting transform encoding of point cloud attribute information.

[0321] Figure 32 is a schematic diagram of the encoding process of a lifting transform. The lifting transform also predicts the attributes of the point cloud based on LOD. The difference from the predictive transform is that the lifting transform first divides the LOD into high and low layers, predicts in the reverse order of the LOD generation layer, and introduces an update operator in the prediction process to update the quantized weights of the low-level LOD midpoints to improve the accuracy of the prediction. This is because the attribute values ​​of the low-level LOD midpoints are frequently used to predict the attribute values ​​of the high-level LOD midpoints, and the points in the low-level LOD should have greater influence.

[0322] Step 1: Segmentation process.

[0323] The segmentation process is to divide the complete LOD layer into a low LOD layer L(N) and a high LOD layer H(N). If a point cloud has three LOD layers, namely (LOD l ) l＝0,1,2 , after segmentation, LOD2 is the high LOD layer, denoted as H(N), (LOD l ) l＝0,1 It is the low LOD layer, denoted as L(N).

[0324] Step 2: Prediction process.

[0325] The point in the high-level LOD selects the attribute information of the nearest neighbor point from the low-level as the attribute prediction value P(N) of the current point to be coded. The prediction residual D(N) is recorded as: D(N) = H(N) - P(N)#

[0326] Step 3: Update process.

[0327] Update the attribute prediction residual D(N) in the high-level LOD to obtain U(N), and use U(N) to improve the attribute value of the midpoint of the low-level LOD, as shown in the following formula: L′(N)=L(N)+U(N)

[0328] The above process will iterate continuously until the lowest LOD according to the order of LOD from high to low.

[0329] Because the LOD-based prediction scheme makes points in the lower LOD layers more influential, the transformation scheme based on the lifting wavelet transform introduces quantization weights and updates the prediction residual based on the prediction residual D(N) and the distance between the prediction point and the adjacent points. Finally, the quantization weights used in the transformation process are used to adaptively quantize the prediction residual. It is important to note that the quantization weight value of each point can be determined by geometric reconstruction at the decoding end, so the quantization weights should not be encoded.

[0330] (c) Region-adaptive hierarchical transformation.

[0331] The Regional Adaptive Hierarchical Transform (RAHT) is a Haar wavelet transform that transforms point cloud attribute information from the spatial domain to the frequency domain, further reducing the correlation between point cloud attributes. Its main concept is to transform the nodes in each layer in the X, Y, and Z dimensions in a bottom-up manner according to the octree structure (as shown in Figure 34), and iterate until the root node of the octree. As shown in Figure 33, the basic concept is to perform a wavelet transform based on the hierarchical structure of the octree, associate attribute information with the octree nodes, and recursively transform the attributes of occupied nodes under the same parent node in a bottom-up manner, transforming the nodes in each layer in the X, Y, and Z dimensions until the root node of the octree is reached. During the hierarchical transformation process, the low-pass / low-frequency (DC) coefficients obtained after the transformation of the nodes in the same layer are passed to the nodes in the next layer for further transformation, while all high-pass / high-frequency (AC) coefficients can be encoded using an arithmetic coder.

[0332] During the transformation process, the DC coefficients (direct current components) of the transformed nodes at the same layer are passed to the previous layer for further transformation, while the AC coefficients (alternating current components) of each layer are quantized and encoded. The main transformation processes are described below.

[0333] FIG35A is a schematic diagram of a RAHT forward transformation process, and FIG35B is a schematic diagram of a RAHT inverse transformation process. For the transformation and inverse transformation process corresponding to RAHT, assuming that g′ L,2x,y,z and g′L,2x+1,y,z are the DC coefficients of two neighboring points in the L layer. After linear transformation, the information of the L-1 layer is the AC coefficient f′ L-1,x,y,z and DC coefficient g′ L-1,x,y,z ; Then, f′ L-1,x,y,z No more transformation will be performed, and quantization coding will be performed directly, g′ L-1,x,y,z The nearest neighbor will continue to be searched for transformation. If no neighbor is found, it will be directly passed to the L-2 layer. That is, the RAHT transformation is only effective for nodes with neighbor points. Nodes without neighbor points will be directly passed to the previous layer. In the above transformation process, g′ L,2x,y,z The weights (the number of non-empty child nodes in the node) corresponding to g′L, 2x+2, y, and z are w′ respectively. L,2x,y,z and w′L,2x+1,y,z (abbreviated as w′0 and w′1), g′ L-1,x,y,z The weight is w′ L-1,x,y,z , then the general transformation formula is:

[0334] Among them, T w0,w1 is the transformation matrix:

[0335] The transformation matrix will be updated as the weights corresponding to each point change adaptively. The above process will be iterated and updated continuously according to the partitioning structure of the octree until the root node of the octree is reached.

[0336] In a specific implementation method, for regional adaptive hierarchical intra-frame prediction transform coding, prediction can be performed based on RAHT transform coding. As shown in Figure 33, RAHT attribute transform is based on the order of the octree hierarchy, and the transformation is continuously performed from the voxel level until the root node is obtained, thereby completing the hierarchical transform coding of the entire attribute. In the prediction transform coding, attribute prediction transform coding is also performed based on the hierarchical order of the octree, but the transformation is continuously performed from the root node to the voxel level. In each RAHT attribute transformation process, attribute prediction transform coding is performed based on a 2×2×2 block. The specific example is shown in Figure 36. As shown in Figure 36, it can be seen that the grid filling block is the current block to be encoded, and the diagonal filling block is some neighboring blocks that are coplanar and colinear with the current block to be encoded. Among them, the attributes of the current block are normalized in the following way: A node =∑ p∈node attribute(p); w node =∑ p∈node 1={p∈node}; a node =A node / w node .

[0337] First, the attributes of the current block can be obtained by the attributes of the points contained in the current block, namely: A node By simply adding the attributes of the points in the current block, and then normalizing the attributes of the current block with the number of points in the current block, the mean value a of the current block attribute is obtained. node The attribute transform coding is performed using the mean value of the current block attribute. The specific coding process is shown in Figure 37.

[0338] As shown in Figure 37, the overall process of RAHT attribute prediction transform coding is shown. (a) is the current block and some coplanar and colinear neighboring blocks, (b) is the normalized block, (c) is the upsampled block, (d) is the attribute of the current block, and (e) is the attribute of the predicted block obtained by linear weighted fitting using the neighboring attributes of the current block. Finally, attribute transformation is performed on both to obtain DC and AC coefficients, and the AC coefficients are predictively coded.

[0339] The predicted attributes of the current block can be obtained by linear fitting as shown in Figure 38. As shown in Figure 38, 19 neighboring blocks of the current block are first obtained. Then, the spatial geometric distance between the neighboring blocks and each sub-block of the current block is used to perform a linear weighted prediction of the attributes of each sub-block. Finally, the predicted block attributes obtained using the linear weighting are transformed. The specific attribute transformation is shown in Figure 39.

[0340] In Figure 39, (d) represents the original value of the attribute, and the corresponding attribute transformation coefficient is as follows:

[0341] (e) represents the attribute prediction value, and the corresponding attribute transformation coefficient is as follows:

[0342] By subtracting the original value of the attribute from the predicted value of the attribute, the prediction residual can be obtained as follows:

[0343] In another specific implementation, for region-adaptive hierarchical inter-frame prediction transform coding, two region-adaptive hierarchical inter-frame prediction transform coding schemes may be included, as follows:

[0344] 1. Region Adaptive Hierarchical Inter-frame Prediction Transform Coding Scheme 1

[0345] In the first regionally adaptive hierarchical inter-frame prediction transform coding scheme, the process is similar to intra-frame prediction coding. First, the RAHT attribute transform coding structure is constructed based on geometric information. That is, the transformation is continuously performed at the voxel level until the root node is obtained, thus completing the hierarchical transform coding of the entire attribute. In this way, the intra-frame coding structure and inter-frame attribute coding structure are constructed, as shown in Figure 40.

[0346] As shown in FIG40 , firstly, the geometric information of the current node to be encoded (ie, the current node) is used to obtain the co-located node of the current node in the reference frame, and then the geometric information and attribute information of the reference node are used to obtain the predicted attribute of the current node.

[0347] Among them, the attribute prediction value of the current node is obtained according to the following two different methods:

[0348] 1. The inter-frame prediction node of the current node is valid: that is, if the same-position node exists, the attribute of the same-position node is directly used as the attribute prediction value of the current node;

[0349] 2. The inter-frame prediction node of the current node is invalid: that is, the co-located node does not exist, then the attribute prediction value of the adjacent node in the frame of the current node is used as the attribute prediction value of the current node.

[0350] Finally, the attribute prediction value is used to predict the attribute of the current node, thus completing the prediction coding of the entire attribute.

[0351] 2. Region Adaptive Hierarchical Inter-frame Prediction Transform Coding Scheme 2

[0352] In the regional adaptive hierarchical inter-frame prediction transform coding scheme 1, unlike the intra-frame prediction and inter-frame prediction coding scheme 1, if the inter-frame prediction coding scheme 2 is started, the RAHT attribute transform coding structure will be constructed based on the geometric information of the current node first, that is, the nodes will be continuously merged at the voxel level until the root node of the entire RAHT transform tree is obtained, thereby completing the transform coding hierarchical structure of the entire attribute. Secondly, according to the RAHT transform structure, the root node is divided to obtain N child nodes (N is less than or equal to 8) of each node. In the inter-frame prediction coding scheme 2, the attributes of the N child nodes will first be independently orthogonally transformed using the RAHT transform to obtain the DC and AC coefficients of each child node. Secondly, the AC coefficients of the N child nodes are predicted for attribute inter-frame according to the following method:

[0353] 1. The inter-frame prediction node of the current node is valid: that is, if the same-position node exists, the attribute of the same-position node is directly used as the attribute prediction value of the current node.

[0354] 2. If the current node can find a node in the reference frame cache that is exactly the same as the current node's position, that is, the co-located node exists. In this case, the AC coefficients of the M child nodes contained in the co-located node are directly used as the predicted AC coefficient attributes of the current node's N child nodes. If the AC coefficients of the co-located node corresponding to the child node do not exist, prediction cannot be started.

[0355] a. If the AC coefficient of the child node contained in the same node is not zero: the AC coefficient of the child node is directly used as the predicted value of the child node at the corresponding position of the current node.

[0356] b. If the AC coefficient of the child node contained in the same-position node is zero, the AC coefficient of the corresponding child node of the intra-frame prediction will be used as the predicted value of the child node at the corresponding position of the current node.

[0357] 3. The inter-frame prediction node of the current node is invalid: that is, the co-located node does not exist, then the attribute prediction value of the adjacent node in the frame of the current node is used as the attribute prediction value of the current node.

[0358] At present, in the common G-PCC RAHT attribute encoding and decoding, the inter / intra prediction encoding and decoding of each node in the point cloud in the current point cloud sequence is performed by deciding whether to use RAHT prediction transform coding in high-level syntax elements, such as syntax elements at the point cloud sequence level. In addition, a syntax element, such as treeDepth, is used to determine the starting layer of inter-frame prediction encoding and decoding. In the following RAHT encoding and decoding layer, only RAHT intra-frame prediction encoding and decoding is used. In the current RAHT coding scheme, the number of neighboring nodes N of the current node is first used to determine whether it is greater than a certain threshold. When the number of neighboring nodes N of the current node is greater than a certain threshold, the AC coefficient of the current node is predicted (intra-frame or inter-frame prediction). When the number of neighboring nodes N of the current node is less than a certain threshold, it is considered that the current node does not meet the conditions for prediction coding, and only the attribute transformation of the current node is performed. The current coding and decoding scheme is mainly to utilize the spatial correlation of the current node, especially the geometric spatial correlation of the neighborhood of the current node to improve coding efficiency. However, this encoding scheme does not take into account the inherent distribution characteristics of the attribute information of each node, but directly determines the RAHT encoding scheme for the entire point cloud sequence at the sequence level. Secondly, when starting the predictive transform coding scheme, it only determines the encoding method of the current node based on the neighborhood geometric spatial correlation of the current node, and does not effectively combine the attribute distribution characteristics of the current node, resulting in low encoding efficiency of the attribute information.

[0359] To address the above issues, the embodiments of the present application comprehensively consider the attribute distribution characteristics and spatial distribution characteristics of each node. The encoder encodes each node in the current layer using at least one RAHT encoding method, determines at least one encoding cost corresponding to each node, and then determines the optimal encoding mode for the current layer based on the at least one encoding cost corresponding to each node and passes it to the decoder. The decoder selects a decoding mode based on the RAHT encoding mode corresponding to the current layer for decoding. In this way, by adaptively selecting the optimal encoding and decoding mode from multiple encoding and decoding modes, the efficiency of RAHT attribute encoding and the decoding efficiency of point cloud attribute information are improved, thereby improving point cloud decoding performance.

[0360] The embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0361] In one embodiment of the present application, referring to FIG41 , a schematic flow chart of a point cloud encoding method provided by an embodiment of the present application is shown. As shown in FIG41 , the method may include:

[0362] S101. Encode attribute information of a node in a current layer using at least one area adaptive layered transform (RAHT) coding mode, and determine at least one coding cost and at least one candidate attribute coding information corresponding to the node.

[0363] It should be noted that the encoding method of the embodiment of the present application specifically refers to a point cloud encoding method, which can be applied to a point cloud encoder (also referred to as "encoder" for short).

[0364] Accordingly, in an embodiment of the present application, the current layer may be a RAHT transform layer to be encoded. The encoder may construct a RAHT attribute transform coding structure corresponding to the point cloud based on the geometric information of the nodes in the point cloud.

[0365] In an embodiment of the present application, it is necessary to first construct a RAHT attribute transformation coding structure based on the geometric information of the points in the point cloud. Specifically, based on the octree structure corresponding to the point cloud, the voxel level can be continuously merged until the root node is obtained, thereby completing the transformation coding hierarchical structure of the entire attribute and obtaining the RAHT attribute transformation coding structure.

[0366] In some embodiments, the encoder may perform downsampling along each spatial coordinate axis starting from a root node based on a RAHT attribute transform coding structure to determine at least one RAHT transform layer corresponding to the point cloud. Here, the at least one RAHT transform layer includes the current layer.

[0367] Exemplarily, a RAHT attribute transformation coding structure may be defined, where a layer obtained by downsampling in a preset direction, such as the Z direction, the Y direction, and the X direction, is a RAHT transformation layer, such as the current layer.

[0368] It should be noted that, in the embodiment of the present application, for the current layer, the current layer may include at least one point. In particular, when encoding the current layer, the at least one point in the current layer may be used as a node to be encoded in the current layer.

[0369] Furthermore, in an embodiment of the present application, for each point in the current layer, it corresponds to a geometric information and an attribute information; wherein the geometric information represents the spatial relationship of the point, and the attribute information represents the relevant information of the attribute of the point.

[0370] Here, the attribute information may be color information, or reflectivity, or other attributes, which are not specifically limited in the embodiments of the present application. Specifically, when the attribute information is color information, it may be color information in any color space. For example, the attribute information may be color information in an RGB space, a YUV space, a YCbCr space, or the like, which are not specifically limited in the embodiments of the present application.

[0371] In an embodiment of the present application, attribute information of a node in a current layer is encoded through at least one regional adaptive layered transform (RAHT) coding mode to determine at least one coding cost and at least one candidate attribute coding information corresponding to the node.

[0372] In an embodiment of the present application, at least one region-adaptive hierarchical transform (RAHT) coding mode may include the aforementioned RAHT transform coding mode, RAHT intra-frame prediction transform coding mode, and RAHT inter-frame prediction transform coding mode. The encoder encodes the attribute information of each node in the current layer using at least one region-adaptive hierarchical transform (RAHT) coding mode, and determines the coding cost and coding information corresponding to each RAHT coding mode. The encoder uses the coding information corresponding to each RAHT coding mode as candidate attribute coding information, thereby obtaining at least one coding cost and at least one candidate attribute coding information corresponding to each node.

[0373] It should be noted that in an embodiment of the present application, the RAHT transform coding mode can perform attribute transform coding based on the order of the octree hierarchy. The encoder can continuously perform transform coding from the voxel level until the root node is obtained based on the hierarchical order of the octree, thereby completing the RAHT transform coding of the attribute information of each node in the point cloud. In the RAHT prediction transform coding mode, such as the RAHT intra-frame prediction transform coding mode and the RAHT inter-frame prediction transform coding mode, it can also be based on the hierarchical order of the octree, but the encoding is continuously performed from the root node to the voxel level.

[0374] In some embodiments, the encoder may pre-set a buffer space corresponding to at least one RAHT coding mode, and store the candidate attribute coding information corresponding to each RAHT coding mode in the corresponding buffer space. For example, the encoder may set a buffer 1 corresponding to the RAHT transform coding mode, a buffer 2 corresponding to the RAHT intra-frame prediction transform coding mode, and a buffer 3 corresponding to the RAHT inter-frame prediction transform coding mode. The encoder encodes the attribute information of the current node using the RAHT transform coding mode, the RAHT intra-frame prediction transform coding mode, and the RAHT inter-frame prediction transform coding mode, respectively, and stores the candidate attribute coding information corresponding to the RAHT transform coding mode in buffer 1, the candidate attribute coding information corresponding to the RAHT intra-frame prediction transform coding mode in buffer 2, and the candidate attribute coding information corresponding to the RAHT inter-frame prediction transform coding mode in buffer 3.

[0375] S102: Determine a RAHT coding mode corresponding to a current layer based on at least one coding cost corresponding to a node, and determine attribute coding information corresponding to the node from at least one candidate attribute coding information.

[0376] In an embodiment of the present application, the encoder may evaluate the coding performance of at least one RAHT coding mode for the current node based on at least one coding cost corresponding to the node, and determine the attribute coding information corresponding to the node from at least one candidate attribute coding information.

[0377] In some embodiments, the encoder may determine the sum of the coding costs of each RAHT coding mode for all nodes in the current layer based on at least one coding cost corresponding to each node in the current layer. Based on the sum of the coding costs of each RAHT coding mode, the RAHT coding mode with the smallest sum of the coding costs is determined as the RAHT coding mode corresponding to the current layer. Furthermore, for each node in the current layer, the encoder determines, from the at least one candidate attribute coding information corresponding to each node, candidate attribute coding information corresponding to the RAHT coding mode corresponding to the current layer as the attribute coding information corresponding to each node.

[0378] That is, the encoder may determine the best coding mode for the current layer according to at least one coding cost corresponding to each node, as the RAHT coding mode corresponding to the current layer.

[0379] In some embodiments, the encoder may determine, in at least one cache corresponding to at least one RAHT coding mode, the candidate attribute coding information of each node stored in the cache corresponding to the RAHT coding mode corresponding to the current layer as the attribute coding information corresponding to each node.

[0380] S103 : Generate a bitstream based on the RAHT coding mode corresponding to the current layer and the attribute coding information corresponding to the node.

[0381] In an embodiment of the present application, the encoder can determine the attribute coding information corresponding to the current layer based on the attribute coding information corresponding to each node in the current layer. The encoder can determine the RAHT coding mode flag corresponding to the current layer based on the RAHT coding mode corresponding to the current layer. The RAHT coding mode flag is used to indicate the RAHT transform coding mode or the RAHT prediction transform coding mode; the RAHT prediction transform coding mode includes: inter-frame prediction transform coding mode or intra-frame prediction transform coding mode.

[0382] The encoder performs the same processing on each RAHT transform layer in the point cloud to determine the coding mode flag and attribute coding information corresponding to each RAHT transform layer. The encoder generates a bitstream based on the coding mode flag and attribute coding information corresponding to each RAHT transform layer.

[0383] In this way, the encoder sends the code stream to the decoder, and the decoder can determine the decoding method for each RAHT transform layer according to the coding mode flag corresponding to each RAHT transform layer of the point cloud in the code stream; and decode the attribute coding information corresponding to each RAHT transform layer according to the decoding method for each RAHT transform layer.

[0384] In some embodiments, the encoder can add the RAHT prediction coding mode for each RAHT transform layer in the point cloud to the Attribute Brick Header (ABH) parameter set. The decoder uses the ABH to obtain the RAHT prediction coding mode for each RAHT transform layer. This embodiment of the application does not limit the encoding format of the ABH parameter set.

[0385] It is understandable that in the embodiments of the present application, the encoder encodes each node in the current layer using at least one RAHT encoding method, determines at least one encoding cost and at least one candidate attribute encoding information corresponding to each node, and thereby determines the optimal encoding mode for the current layer based on the at least one encoding cost corresponding to each node. This encoding mode is used to determine the attribute encoding information corresponding to each node in the current layer, and the RAHT encoding mode corresponding to the current layer and the attribute encoding information corresponding to the node are transmitted to the decoding end, so that the decoding end can adaptively decode the attribute information of the current layer based on the RAHT encoding mode corresponding to the current layer. In this way, by introducing multiple encoding modes and adaptively selecting the optimal mode in combination with the encoding cost, the attribute distribution characteristics and spatial distribution characteristics of each node are comprehensively considered, the RAHT attribute encoding efficiency and the encoding efficiency of the point cloud attribute information are improved, and thus the point cloud coding performance is improved.

[0386] In some embodiments, the at least one candidate attribute coding information includes: transform coding information and prediction transform coding information; the process in S101 above can be implemented through S1011-S1013, including:

[0387] S1011, by performing RAHT transform encoding on the attribute information of each node in the point cloud, determine the attribute transformation information and transform coding information corresponding to each node in the current layer.

[0388] In some embodiments, the encoder can recursively perform RAHT transformation and encoding on the attribute information of each node in the point cloud based on the RAHT attribute transformation coding structure corresponding to the point cloud, starting from the voxel-level nodes until the root node, to determine the attribute transformation information and transformation coding information corresponding to each node in the point cloud, thereby determining the transformation coding information corresponding to each node in the current layer; the attribute transformation information is determined by performing RAHT transformation on the attribute information; and the transformation coding information is determined by encoding the attribute transformation information.

[0389] For example, the encoder recursively performs a RAHT transform on the attribute information of each node in the point cloud, starting from the voxel-level nodes based on the octree structure, to obtain the DC coefficient and AC coefficient of each node. The DC coefficient is passed to the next layer for further transformation, and the AC coefficient is encoded as the attribute transformation information corresponding to each node to determine the transformation coding information corresponding to each node in the point cloud. In this way, the attribute transformation information and transformation coding information corresponding to each node in the current layer are determined based on the nodes contained in the current layer.

[0390] In some embodiments, the encoder may also determine the N child nodes corresponding to each node in the point cloud based on the RAHT attribute transformation coding structure corresponding to the point cloud, starting from the root node; for the N child nodes corresponding to each node, perform RAHT attribute transformation and encoding on the attribute information of the N child nodes, determine the attribute transformation information and transformation coding information corresponding to the N child nodes, and thus determine the attribute transformation information and transformation coding information corresponding to each node in the point cloud; N is greater than 0 and not greater than a preset child node number threshold; based on the attribute transformation information and transformation coding information corresponding to each node in the point cloud, determine the attribute transformation information and transformation coding information corresponding to each node in the current layer. Exemplarily, the preset child node number threshold can be 8, or it can be set to other values ​​according to actual conditions. The specific selection is based on actual conditions and is not limited in the embodiments of the present application.

[0391] Exemplarily, the encoder can be based on the octree structure and divided from the root node to obtain N child nodes corresponding to each node, where N is greater than 0 and less than or equal to 8. Starting from the root node, the encoder performs independent orthogonal transformation on the N child nodes corresponding to each node to obtain the DC coefficient and AC coefficient of each child node. The DC coefficient is also passed to the next layer for further transformation. The AC coefficient of each child node is encoded as attribute transformation information to determine the transformation coding information corresponding to each child node. In this way, according to the correspondence between the parent node and the child node, the same processing is performed on each node in the octree structure to obtain the attribute transformation information and transformation coding information corresponding to each node in the point cloud. According to the nodes contained in the current layer, the attribute transformation information and transformation coding information corresponding to each node in the current layer are determined.

[0392] S1012: Perform predictive coding on the attribute transformation information corresponding to each node in the current layer to determine the predictive transformation coding information corresponding to each node in the current layer.

[0393] In S1012, the encoder performs predictive coding on the attribute transformation information corresponding to each node in the current layer. Here, if inter-frame prediction is not enabled, the encoder may perform intra-frame prediction coding on each node in the current layer to determine the intra-frame prediction coding information corresponding to each node. If inter-frame prediction is enabled, the encoder may perform intra-frame prediction coding and inter-frame prediction coding on each node in the current layer to determine the intra-frame prediction coding information and inter-frame prediction coding information corresponding to each node.

[0394] It should be noted that before performing RAHT intra / inter prediction transform coding, the encoder will first determine whether the current node meets the RAHT intra / inter prediction transform coding conditions. The encoder determines whether the number of neighboring nodes of the parent node of each node in the current layer is greater than a preset first number threshold; if it is greater than the preset first number threshold, it determines whether the number of neighboring nodes of each node in the current layer is greater than a preset second number threshold; if it is greater than the preset second number threshold, it performs prediction coding on the attribute transformation information corresponding to each node in the current layer to determine the prediction transformation coding information corresponding to each node in the current layer.

[0395] When the number of neighboring nodes of the parent node of each node in the previous layer is not greater than the preset first number threshold, or the number of neighboring nodes of each node in the current layer is not greater than the preset second number threshold, the encoder performs RAHT transform encoding on the current node.

[0396] In some embodiments, for intra-frame prediction coding, the attribute information prediction value corresponding to each node in the current layer can be determined based on the attribute information prediction value of the neighboring nodes of each node in the current layer according to the intra-frame prediction coding method described above. Furthermore, encoding is performed based on the attribute information prediction value corresponding to each node to determine the intra-frame prediction transform coding information corresponding to each node in the current layer. For example, the attribute information prediction value can be an AC coefficient prediction value.

[0397] In some embodiments, inter-frame prediction coding can be implemented by using any one of the above-mentioned inter-frame prediction coding scheme 1 and inter-frame prediction coding scheme 2.

[0398] Exemplarily, if implemented through inter-frame prediction coding scheme one, the encoder can determine the co-located node corresponding to the position of each node in the current layer in the reference point cloud corresponding to the point cloud; based on the reconstructed attribute transformation information of the co-located node, determine the attribute information prediction value corresponding to each node in the current layer; based on the attribute information prediction value, encode the attribute transformation information corresponding to each node in the current layer, and determine the prediction transformation coding information corresponding to each node in the current layer.

[0399] In some embodiments, when there is no co-located node corresponding to a node in the reference point cloud, the attribute information prediction value corresponding to the node is determined through intra-frame prediction based on the reconstructed attribute transformation information of the node's neighboring nodes.

[0400] Exemplarily, if implemented through the second inter-frame prediction coding scheme, the encoder can determine the corresponding co-located node of each node in the current layer in the reference point cloud corresponding to the point cloud; when each node in the current layer is a parent node in the current layer, the attribute information prediction value corresponding to each node in the current layer is determined based on the reconstructed attribute transformation information of the co-located node; when each node in the current layer is a child node in the current layer, the attribute information prediction value corresponding to each node in the current layer is determined based on the reconstructed attribute transformation information of the M child nodes corresponding to the co-located node in the reference point cloud; M is greater than 0 and not greater than the preset child node number threshold; based on the attribute information prediction value, the attribute transformation information corresponding to each node in the current layer is encoded, and the inter-frame prediction transformation coding information corresponding to each node in the current layer is determined.

[0401] Here, for the parent node in the current layer, the encoder directly uses the reconstructed attribute transformation information of the parent node's co-located node in the reference point cloud as the attribute information prediction value corresponding to the parent node. For the N child nodes corresponding to the parent node, the encoder uses the reconstructed attribute transformation information of the M child nodes corresponding to the parent node in the reference point cloud as the attribute information prediction value corresponding to the N child nodes of the parent node based on the co-located node of the parent node in the reference point cloud.

[0402] It should be noted that the reference point cloud is a point cloud whose attribute information has been encoded and reconstructed. For example, the reference point cloud may be a point cloud adjacent to the point cloud of the current layer, whose attribute information has been encoded and reconstructed. In some embodiments, the reconstructed attribute transformation information may be reconstructed AC coefficients.

[0403] In some embodiments, the above-mentioned determination of the attribute information prediction value corresponding to each node in the current layer based on the reconstructed attribute transformation information of the M child nodes corresponding to the co-located node in the reference point cloud can be achieved through the following process:

[0404] Determine the co-located child node corresponding to the position of each child node in the M child nodes; when the reconstructed attribute transformation information of the co-located child node is greater than the preset information value threshold, determine the attribute information prediction value of each node in the current layer based on the reconstructed attribute transformation information of the co-located child node; when the reconstructed attribute transformation information of the co-located child node is less than or equal to the preset information value threshold, determine the attribute information prediction value corresponding to each node in the current layer based on the reconstructed attribute transformation information of the neighboring nodes of each node in the current layer.

[0405] Here, for the N child nodes in the parent node, the encoder determines the child node with the same position among the M child nodes of the co-located node as the co-located child node corresponding to each child node. When the reconstructed attribute transformation information of the co-located child node is greater than the preset information value threshold, such as when the reconstructed AC coefficient of the co-located child node is greater than zero, the reconstructed attribute transformation information of the co-located child node, such as the reconstructed AC coefficient of the co-located child node, is directly used as the attribute information prediction value of each child node. When the reconstructed attribute transformation information of the co-located child node is less than or equal to the preset information value threshold, such as when the reconstructed AC coefficient of the co-located child node is zero, intra-frame prediction is used to determine the attribute information prediction value corresponding to each child node based on the reconstructed attribute transformation information of the neighboring nodes of each child node.

[0406] It should be noted that, in the above process, if the AC coefficient of the co-located child node corresponding to the child node does not exist, intra-frame prediction or inter-frame prediction is not started.

[0407] In some embodiments, when there is no co-located node corresponding to the parent node in the reference point cloud, the attribute information prediction value corresponding to the parent node is determined through intra-frame prediction based on the reconstructed attribute transformation information of the parent node's neighboring nodes.

[0408] In some embodiments, when there is no co-located child node corresponding to the child node in the reference point cloud, the attribute information prediction value corresponding to the child node is determined through intra-frame prediction based on the reconstructed attribute transformation information of the neighboring nodes of the child node.

[0409] It should be noted that in the embodiments of the present application, the RAHT transform coding mode includes two implementations: the RAHT intra-frame prediction transform coding mode and the RAHT inter-frame prediction transform coding mode; the RAHT inter-frame prediction transform coding mode includes two implementations. Therefore, when encoding node attribute information according to at least one RAHT coding mode, the encoder may combine various implementations of the aforementioned coding modes. The specific selection is based on actual circumstances and is not limited in the embodiments of the present application.

[0410] S1013: Determine at least one coding cost corresponding to the node based on the transform coding information and the predicted transform coding information.

[0411] In S1013 , when intra prediction is not enabled, the encoder may perform decoding reconstruction and coding cost calculation based on the transform coding information and the intra prediction transform coding information to determine at least one coding cost corresponding to the node.

[0412] Alternatively, when intra prediction is enabled, the encoder may perform decoding reconstruction and coding cost calculation based on transform coding information, intra prediction transform coding information, and inter prediction transform coding information to determine at least one coding cost corresponding to the node.

[0413] In some embodiments, the encoder can perform decoding and reconstruction based on transform coding information to determine the first rate-distortion cost corresponding to each node in the current layer; perform decoding and reconstruction based on intra-frame prediction transform coding information to determine the second rate-distortion cost corresponding to each node in the current layer; and perform decoding and reconstruction based on inter-frame prediction transform coding information to determine the third rate-distortion cost corresponding to each node in the current layer.

[0414] In this way, the encoder can determine the first coding cost corresponding to the current layer based on the first rate-distortion cost corresponding to each node in the current layer; the first coding cost corresponds to the RAHT transform coding mode; based on the second rate-distortion cost corresponding to each node in the current layer, the second coding cost corresponding to the current layer is determined; the second coding cost corresponds to the RAHT intra-frame prediction transform coding mode; based on the third rate-distortion cost corresponding to each node in the current layer, the third coding cost corresponding to the current layer is determined; the third coding cost corresponds to the RAHT inter-frame prediction transform coding mode; by comparing the first coding cost, the first coding cost, and the third coding cost, the RAHT coding mode corresponding to the current layer is determined.

[0415] For example, in the rate-distortion optimization algorithm, the distortion D between the reconstructed attribute information corresponding to each RAHT coding mode and the original attribute information of the node is first calculated, and then the code rate R required for each RAHT coding mode is obtained. The rate-distortion cost J corresponding to each RAHT coding mode is calculated by the following formula: J = D + λ × R

[0416] Among them, λ can be calculated by attribute quantization parameters. For example, The parameter N can be preset to different values ​​according to reflectivity and color.

[0417] In the above scheme, at least one coding mode is introduced by encoding the attribute information of nodes in the current layer: RAHT transform coding, RAHT intra-frame prediction transform coding, and RAHT inter-frame prediction transform coding. The RAHT coding mode is adaptively selected for all nodes in the current layer by comparing the coding costs of at least one coding mode. In some embodiments, the encoder may also determine the attribute coding mode for the nodes in the current layer by comprehensively analyzing the reconstructed attribute distribution characteristics of the neighboring nodes of the parent node of the node in the current layer.

[0418] In some embodiments, the encoder can determine the RAHT coding mode corresponding to the current layer based on the attribute information of the parent node of the node in the current layer and the reconstructed attribute information of the neighboring nodes of the parent node; use the RAHT coding mode corresponding to the current layer to encode the attribute information of the nodes in the current layer to determine the attribute coding information corresponding to the nodes.

[0419] Exemplarily, when the error between the attribute information of the parent node of the node in the current layer and the reconstructed attribute information of the neighboring nodes of the parent node is greater than a preset error threshold; the RAHT transform coding mode is determined as the RAHT coding mode corresponding to the current layer; the transform coding mode represents the RAHT transform and encoding of the attribute information; when the error between the attribute information of the parent node of the node in the current layer and the reconstructed attribute information of the neighboring nodes of the parent node is less than or equal to the preset error threshold, the RAHT prediction transform coding mode is determined as the RAHT coding mode corresponding to the current layer; the prediction transform coding mode represents the prediction encoding of the attribute transform coefficients determined by the RAHT transform of the attribute information.

[0420] That is, if the error between the attributes of the parent node of the current node and the reconstructed attributes of the neighboring nodes of the parent node of the current node is within a certain range, then the distribution characteristics of the neighborhood attributes of the current node are considered to be relatively flat. Based on this distribution characteristic, it can be implicitly deduced that the RAHT prediction transform coding mode is used for the current node; otherwise, it is considered that the attribute distribution of the neighborhood range of the current node is relatively jittery, and the RAHT transform coding mode will be used. The encoder processes each node of the current layer in the above manner, thereby determining the RAHT coding mode corresponding to the current layer.

[0421] It can be understood that the encoder determines the encoding mode of the nodes in the current layer through the reconstructed attribute distribution characteristics of the parent node's neighborhood nodes, and comprehensively considers the attribute distribution characteristics and spatial distribution characteristics of the nodes, thereby improving the RAHT attribute coding efficiency and the coding efficiency of point cloud attribute information, and thus improving the point cloud coding performance.

[0422] In some embodiments, the encoder can indicate at the point cloud level whether the predictive transform coding mode is enabled for each RAHT transform layer in the point cloud. The encoder can determine the predictive transform enable flag corresponding to the point cloud based on the RAHT coding mode determined for each RAHT transform layer in the point cloud. Here, the predictive transform enable flag indicates whether the predictive transform coding mode is enabled for the RAHT transform layer in the point cloud.

[0423] In some embodiments, the encoder can determine the number of coding mode flags corresponding to the point cloud based on at least one RAHT transform layer in the point cloud for which the RAHT coding mode is determined. The number of coding mode flags is used to inform the decoder of the number of coding mode flags to be decoded. The encoder writes at least one of the prediction enable transform flag and the number of coding mode flags into the bitstream and sends it to the decoder.

[0424] In some embodiments, the encoder may divide the nodes in the current layer into at least two node groups; for each node group in the at least two node groups, based on at least one coding cost corresponding to each node in each node group, determine at least one coding cost corresponding to each node group; based on the at least one coding cost corresponding to each node group, determine the RAHT coding mode corresponding to each node group; based on the RAHT coding mode corresponding to each node group, determine the attribute coding information corresponding to each node in each node group, thereby determining the attribute coding information corresponding to each node group; based on the RAHT coding mode corresponding to each node group and the attribute coding information corresponding to each node group, determine at least two groups of attribute coding information corresponding to the current layer and the RAHT coding mode corresponding to each group of attribute coding information, and generate a code stream.

[0425] For example, the encoder can implement attribute information for the nodes of the current layer by dividing the nodes in the current layer into at least two node groups, such as the division of AC coefficient groups, to obtain at least two AC coefficient groups corresponding to the current layer. The encoder selects the best coding mode for each coefficient group and transmits the coding mode corresponding to each coefficient group to the decoder so that the decoder can reconstruct the attribute information of each coefficient group.

[0426] It can be understood that the encoder divides the nodes in the current layer into at least two node groups, performs encoding and encoding cost comparison of at least one RAHT encoding method on each node group, determines the best encoding mode for each node group and passes it to the decoder, thereby further improving the RAHT attribute coding efficiency and the coding efficiency of point cloud attribute information, thereby improving the point cloud coding performance.

[0427] In one embodiment of the present application, referring to FIG42 , a schematic flow chart of a point cloud decoding method provided by an embodiment of the present application is shown. As shown in FIG42 , the method may include:

[0428] S201: Parse the code stream to determine the RAHT coding mode corresponding to the current layer and the attribute coding information corresponding to the nodes in the current layer.

[0429] It should be noted that the decoding method of the embodiment of the present application specifically refers to a point cloud decoding method, which can be applied to a point cloud decoder (also referred to as a "decoder").

[0430] In an embodiment of the present application, as described in the method of the above-mentioned encoder, the RAHT coding mode corresponding to the current layer is that the encoder encodes the attribute information of the node of the current layer through at least one region adaptive layered transform RAHT coding mode, determines at least one coding cost corresponding to the node, and is determined based on the at least one coding cost corresponding to the node.

[0431] In some embodiments, the decoder can obtain the RAHT coding mode flag corresponding to the current layer by parsing the bitstream, and determine the RAHT coding mode corresponding to the current layer according to the RAHT coding mode flag; wherein the RAHT coding mode flag is used to represent the RAHT transform coding mode or the RAHT prediction transform coding mode.

[0432] In an embodiment of the present application, the decoder can determine the RAHT prediction coding mode for each RAHT transform layer in the point cloud by parsing the bitstream corresponding to the point cloud. In this way, when decoding the current layer, the RAHT prediction coding mode corresponding to the current layer can be determined. For example, the decoder can obtain the RAHT prediction coding mode for each RAHT transform layer in the point cloud by decoding the ABH parameter set in the bitstream.

[0433] In some embodiments, the decoder determines the prediction transform enable flag corresponding to the point cloud by parsing the code stream; the prediction transform enable flag indicates whether the prediction transform coding mode is enabled for the point cloud; when the prediction transform enable flag indicates that the prediction transform coding mode is enabled, the number of coding mode flags corresponding to the point cloud is determined.

[0434] In some embodiments, the decoder can determine the number of coding mode flags corresponding to the point cloud by parsing the bitstream; the point cloud is the point cloud where the current layer is located; according to the number of coding mode flags, the RAHT coding mode flag in the bitstream is parsed to determine the RAHT coding mode flag corresponding to each layer in the point cloud.

[0435] For example, the prediction transform enable flag can be determined by the disableAttrInterPred flag at the point cloud level in the bitstream. The number of coding mode flags can be determined by the attr_code_mode_cnt field in the bitstream.

[0436] S202: Based on the RAHT coding mode corresponding to the current layer, decode and reconstruct the attribute coding information corresponding to the node in the current layer to determine the reconstructed attribute information corresponding to the node.

[0437] In the embodiment of the present application, the current layer may be a RAHT transformed layer to be decoded.

[0438] In an embodiment of the present application, it is necessary to first construct a RAHT attribute transformation coding structure based on the geometric information of the points in the point cloud. Specifically, based on the octree structure corresponding to the point cloud, the voxel level can be continuously merged until the root node is obtained, thereby completing the transformation coding hierarchical structure of the entire attribute and obtaining the RAHT attribute transformation coding structure.

[0439] In the embodiment of the present application, it can be defined that a layer obtained by downsampling in a preset direction, such as the Z direction, the Y direction, and the X direction, is a RAHT transformation layer, such as the current layer.

[0440] It should be noted that, in the embodiment of the present application, for the current layer, the current layer may include at least one point. In particular, when decoding the current layer, the at least one point in the current layer may serve as a node to be decoded in the current layer.

[0441] Furthermore, in an embodiment of the present application, for each point in the current layer, it corresponds to a geometric information and an attribute information; wherein the geometric information represents the spatial relationship of the point, and the attribute information represents the relevant information of the attribute of the point.

[0442] Here, the attribute information may be color information, or reflectivity, or other attributes, which are not specifically limited in the embodiments of the present application. Specifically, when the attribute information is color information, it may be color information in any color space. For example, the attribute information may be color information in an RGB space, a YUV space, a YCbCr space, or the like, which are not specifically limited in the embodiments of the present application.

[0443] In some embodiments, the RAHT coding mode may include: a RAHT transform coding mode and a RAHT prediction transform coding mode.

[0444] When the RAHT coding mode is the RAHT transform coding mode, the decoder determines the RAHT transform decoding mode as the corresponding decoding mode, performs RAHT transform decoding on the attribute coding information, and determines the reconstructed attribute information corresponding to the node; wherein the RAHT transform coding mode represents that the encoder performs RAHT transform and encoding on the attribute information of the node.

[0445] Exemplarily, when the RAHT coding mode is the RAHT transform coding mode, the decoder performs entropy decoding on the attribute coding information corresponding to each node in the current layer to obtain attribute transform information corresponding to each node, such as the AC coefficient corresponding to each node. The decoder performs an inverse RAHT transform on the attribute transform information corresponding to each node, such as the AC coefficient, to obtain reconstructed attribute information.

[0446] When the RAHT coding mode is the RAHT prediction transform coding mode, the decoder predicts the attribute transformation information corresponding to the nodes in the current layer and determines the attribute information prediction value corresponding to the nodes in the current layer; based on the attribute information prediction value, the attribute coding information is RAHT transformed and decoded to determine the reconstructed attribute information corresponding to the nodes in the current layer; wherein, the RAHT prediction transform coding represents that the encoder performs RAHT transform on the attribute information of the node, and predictively encodes the attribute transformation information determined by the RAHT transform.

[0447] Exemplarily, when the RAHT coding mode is the RAHT predictive transform coding mode, the decoder decodes the attribute coding information of the node to obtain residual information, and performs intra-frame / inter-frame prediction on the attribute transform information of the node to determine the attribute information prediction value. Exemplarily, the attribute information prediction value may be an AC coefficient prediction value. The decoder determines reconstructed attribute transform information based on the residual and the attribute information prediction value, such as reconstructed AC coefficients, and performs a RAHT inverse transform on the reconstructed attribute transform information to obtain the reconstructed attribute information.

[0448] In some embodiments, the RAHT prediction transform coding mode includes an inter-frame prediction transform coding mode or an intra-frame prediction transform coding mode. The encoder determines a corresponding RAHT prediction transform decoding mode based on the inter-frame prediction transform coding mode or the intra-frame prediction transform coding mode, and decodes the attribute coding information corresponding to each node in the current layer.

[0449] It can be understood that in the embodiment of the present application, the decoder decodes and reconstructs the attribute coding information corresponding to the nodes in the current layer according to the RAHT coding mode transmitted by the encoder, and determines the reconstructed attribute information corresponding to the nodes. Since the RAHT coding mode corresponding to the current layer is that the encoder comprehensively considers the attribute distribution characteristics and spatial distribution characteristics of each node, encodes each node in the current layer through at least one RAHT coding method, determines at least one coding cost corresponding to each node, and determines the best coding mode for the current layer based on the at least one coding cost corresponding to each node. The decoder selects a decoding mode corresponding to the RAHT coding mode corresponding to the current layer for decoding, thereby adaptively decoding the attribute information of the current layer according to the RAHT coding mode corresponding to the current layer. In this way, by adaptively selecting the best coding and decoding mode among multiple coding and decoding modes, the RAHT attribute coding efficiency and the decoding efficiency of the point cloud attribute information are improved, thereby improving the point cloud decoding performance.

[0450] In some embodiments, the RAHT prediction transform coding mode includes: a RAHT intra-frame prediction transform coding mode; when the RAHT coding mode is an intra-frame prediction transform coding mode, the decoder determines the attribute information prediction value corresponding to the node in the current layer based on the attribute information prediction value corresponding to the neighboring node of the node in the current layer.

[0451] In some embodiments, when the RAHT coding mode is an inter-frame prediction transform coding mode, the decoder can determine the co-located node corresponding to the position of the node in the current layer in the reference point cloud; and determine the attribute information prediction value corresponding to the node in the current layer based on the reconstructed attribute transform information of the co-located node. If there is no co-located node, the attribute information prediction value corresponding to the node in the current layer is determined based on the attribute information prediction value corresponding to the neighboring nodes of the node in the current layer.

[0452] In some embodiments, the RAHT prediction transform coding mode includes: a RAHT intra-frame prediction transform coding mode; when the RAHT coding mode is an intra-frame prediction transform coding mode, the decoder determines the attribute information prediction value corresponding to the node in the current layer based on the attribute information prediction value corresponding to the neighboring node of the node in the current layer.

[0453] Here, the decoder

[0454] It should be noted that, in some embodiments, before the decoder uses the RAHT intra / inter prediction decoding mode to decode the node, it first determines whether the number of neighboring nodes of the parent node of each node in the current layer is greater than a preset first number threshold; if it is greater than the preset first number threshold, it determines whether the number of neighboring nodes of each node in the current layer is greater than a preset second number threshold; if it is greater than the preset second number threshold, it indicates that the RAHT intra / inter prediction decoding mode can be enabled to decode the node. The decoder determines the decoding mode corresponding to each node in the current layer based on the RAHT encoding mode corresponding to the current layer. Otherwise, that is, if the number of neighboring nodes of the parent node of each node in the current layer is not greater than the preset first number threshold, or if the number of neighboring nodes of each node in the current layer is not greater than the preset second number threshold, the decoder performs RAHT transform decoding on each node in the current layer.

[0455] In some embodiments, corresponding to the encoder grouping nodes in the current layer to determine the RAHT coding mode, the decoder determines at least two groups of attribute coding information corresponding to the current layer and the RAHT coding mode corresponding to each of the at least two groups of attribute coding information by parsing the bitstream; the at least two groups of attribute coding information correspond to at least two node groups; the at least two node groups are obtained by dividing the nodes in the current layer; the RAHT coding mode corresponding to each group of attribute coding information is determined based on at least one coding cost corresponding to each node group; the at least one coding cost is a coding cost corresponding to at least one RAHT coding mode; according to the RAHT coding mode corresponding to each group of attribute coding information, each group of attribute coding information is decoded and reconstructed to determine the reconstructed attribute information corresponding to each group of attribute coding information, thereby determining the reconstructed attribute information corresponding to the node in the current layer.

[0456] It can be understood that the decoder decodes the attribute coding information corresponding to each node group according to the RAHT coding mode corresponding to each node group in the current layer transmitted by the encoder, and obtains the reconstructed attribute information corresponding to each node group. Since the RAHT coding mode corresponding to each node group is determined by the encoder by comparing the encoding and encoding cost of at least one RAHT coding method for each node group, the optimal coding mode is determined for each node group, thereby further improving the RAHT attribute coding efficiency and the coding efficiency of the point cloud attribute information, thereby improving the point cloud coding performance.

[0457] Based on the above embodiment, in yet another embodiment of the present application, based on the same inventive concept as the above embodiment, FIG43 is a schematic diagram of the composition structure of an encoder. As shown in FIG43 , the encoder 20 may include:

[0458] The encoding part 211 is configured to encode attribute information of a node in a current layer by using at least one region adaptive layered transform (RAHT) coding mode, and determine at least one coding cost and at least one candidate attribute coding information corresponding to the node;

[0459] The determining part 212 is configured to determine a RAHT coding mode corresponding to the current layer based on at least one coding cost corresponding to the node, and determine attribute coding information corresponding to the node from at least one candidate attribute coding information;

[0460] The generating part 213 is configured to generate a code stream based on the RAHT coding mode corresponding to the current layer and the attribute coding information corresponding to the node.

[0461] In some embodiments, the at least one candidate attribute coding information includes: transform coding information and predicted transform coding information; the coding part 211 is also configured to determine the attribute transform information and transform coding information corresponding to each node in the current layer by performing RAHT transform coding on the attribute information of each node in the point cloud; perform predictive coding on the attribute transform information corresponding to each node in the current layer to determine the predicted transform coding information corresponding to each node in the current layer; and determine at least one coding cost corresponding to the node based on the transform coding information and the predicted transform coding information.

[0462] In some embodiments, the encoding part 211 is also configured to determine whether the number of neighboring nodes of the parent node of each node in the current layer is greater than a preset first number threshold; if it is greater than the preset first number threshold, determine whether the number of neighboring nodes of each node in the current layer is greater than a preset second number threshold; if it is greater than the preset second number threshold, perform predictive encoding on the attribute transformation information corresponding to each node in the current layer, and determine the predicted transformation coding information corresponding to each node in the current layer.

[0463] In some embodiments, the encoding part 211 is also configured to recursively perform RAHT transformation and encoding on the attribute information of each node in the point cloud based on the RAHT attribute transformation coding structure corresponding to the point cloud, starting from the voxel-level node until the root node, to determine the attribute transformation information and transformation coding information corresponding to each node in the point cloud, thereby determining the transformation coding information corresponding to each node in the current layer; the attribute transformation information is determined by performing RAHT transformation on the attribute information; and the transformation coding information is determined by encoding the attribute transformation information.

[0464] In some embodiments, the prediction transformation coding information includes: inter-frame prediction transformation coding information; the coding part 211 is also configured to perform inter-frame prediction coding on the attribute transformation information corresponding to each node in the current layer, and determine the inter-frame prediction transformation coding information corresponding to each node in the current layer.

[0465] In some embodiments, the prediction transform coding information includes: intra-frame prediction transform coding information; the determination part 212 is also configured to perform intra-frame prediction coding on the attribute transformation information corresponding to each node in the current layer, and determine the intra-frame prediction transform coding information corresponding to each node in the current layer.

[0466] In some embodiments, the encoding part 211 is further configured to determine the N child nodes corresponding to each node in the point cloud based on the RAHT attribute transformation coding structure corresponding to the point cloud, starting from the root node; for the N child nodes corresponding to each node, RAHT attribute transformation and encoding are performed on the attribute information of the N child nodes to determine the attribute transformation information and transformation coding information corresponding to the N child nodes, thereby determining the attribute transformation information and transformation coding information corresponding to each node in the point cloud; N is greater than 0 and not greater than a preset child node number threshold; based on the attribute transformation information and transformation coding information corresponding to each node in the point cloud, the attribute transformation information and transformation coding information corresponding to each node in the current layer are determined.

[0467] In some embodiments, the encoding part 211 is further configured to determine the co-located node corresponding to the position of each node in the current layer in the reference point cloud corresponding to the point cloud; determine the attribute information prediction value corresponding to each node in the current layer based on the reconstructed attribute transformation information of the co-located node; encode the attribute transformation information corresponding to each node in the current layer based on the attribute information prediction value, and determine the inter-frame prediction transformation coding information corresponding to each node in the current layer.

[0468] In some embodiments, the encoding part 211 is further configured to determine the corresponding co-located node of each node in the current layer in the reference point cloud corresponding to the point cloud; when each node in the current layer is a parent node in the current layer, based on the reconstructed attribute transformation information of the co-located node, determine the attribute information prediction value corresponding to each node in the current layer; when each node in the current layer is a child node in the current layer, based on the reconstructed attribute transformation information of the M child nodes corresponding to the co-located node in the reference point cloud, determine the attribute information prediction value corresponding to each node in the current layer; M is greater than 0 and not greater than a preset child node number threshold; based on the attribute information prediction value, encode the attribute transformation information corresponding to each node in the current layer, and determine the inter-frame prediction transformation encoding information corresponding to each node in the current layer.

[0469] In some embodiments, each node in the current layer includes: a child node in the current layer; the encoding part 211 is also configured to determine the co-located child node corresponding to the position of each child node in the M child nodes; when the reconstructed attribute transformation information of the co-located child node is greater than a preset information value threshold, the attribute information prediction value of each node in the current layer is determined according to the reconstructed attribute transformation information of the co-located child node; when the reconstructed attribute transformation information of the co-located child node is less than or equal to the preset information value threshold, the attribute information prediction value corresponding to each child node is determined based on the reconstructed attribute transformation information of the neighboring nodes of each child node.

[0470] In some embodiments, the encoding part 211 is also configured to determine the attribute information prediction value corresponding to each node in the current layer based on the attribute information prediction value of the neighboring nodes of each node in the current layer when there is no co-located node with a corresponding position in the reference point cloud corresponding to the point cloud.

[0471] In some embodiments, the prediction transform coding information includes: intra-frame prediction transform coding information and inter-frame prediction transform coding information; the at least one coding cost includes: a first rate-distortion cost, a second rate-distortion cost and a third rate-distortion cost. The coding part 211 is also configured to perform decoding and reconstruction based on the transform coding information to determine the first rate-distortion cost corresponding to each node in the current layer; perform decoding and reconstruction based on the intra-frame prediction transform coding information to determine the second rate-distortion cost corresponding to each node in the current layer; perform decoding and reconstruction based on the inter-frame prediction transform coding information to determine the third rate-distortion cost corresponding to each node in the current layer.

[0472] In some embodiments, the determination part 212 is further configured to determine a first coding cost corresponding to the current layer based on a first rate-distortion cost corresponding to each node in the current layer; the first coding cost corresponds to a RAHT transform coding mode; based on a second rate-distortion cost corresponding to each node in the current layer, the second coding cost corresponding to the current layer is determined; the second coding cost corresponds to a RAHT intra-frame prediction transform coding mode; based on a third rate-distortion cost corresponding to each node in the current layer, the third coding cost corresponding to the current layer is determined; the third coding cost corresponds to a RAHT inter-frame prediction transform coding mode; and by comparing the first coding cost, the first coding cost, and the third coding cost, the RAHT coding mode corresponding to the current layer is determined.

[0473] In some embodiments, the determination part 212 is further configured to determine the RAHT coding mode corresponding to the current layer based on the attribute information of the parent node of the node of the current layer and the reconstructed attribute information of the neighboring nodes of the parent node; use the RAHT coding mode corresponding to the current layer to encode the attribute information of the nodes in the current layer to determine the attribute coding information corresponding to the nodes.

[0474] In some embodiments, the determination part 212 is further configured to, when the error between the attribute information of the parent node of the node in the current layer and the reconstructed attribute information of the neighboring nodes of the parent node is greater than a preset error threshold; determine the RAHT transform coding mode as the RAHT coding mode corresponding to the current layer; the transform coding mode represents the RAHT transform and encoding of the attribute information; when the error between the attribute information of the parent node of the node in the current layer and the reconstructed attribute information of the neighboring nodes of the parent node is less than or equal to the preset error threshold, determine the RAHT prediction transform coding mode as the RAHT coding mode corresponding to the current layer; the prediction transform coding mode represents the prediction encoding of the attribute transform coefficients determined by the RAHT transform of the attribute information.

[0475] In some embodiments, the generating part 213 is further configured to determine the RAHT coding mode flag corresponding to the current layer according to the RAHT coding mode corresponding to the current layer; the RAHT coding mode flag is used to represent the RAHT transform coding mode or the RAHT prediction transform coding mode; the RAHT prediction transform coding mode includes: inter-frame prediction transform coding mode or intra-frame prediction transform coding mode; based on the attribute coding information corresponding to the node, determine the attribute coding information corresponding to the current layer; by processing each RAHT transform layer in the point cloud, determine the coding mode flag corresponding to each RAHT transform layer and the attribute coding information corresponding to each RAHT transform layer; generate the code stream based on the coding mode flag corresponding to each RAHT transform layer and the attribute coding information corresponding to each RAHT transform layer.

[0476] In some embodiments, the encoding part 211 is further configured to perform downsampling along each spatial coordinate axis starting from the root node based on the RAHT attribute transformation coding structure, and determine at least one RAHT transformation layer corresponding to the point cloud; the at least one RAHT transformation layer includes the current layer.

[0477] In some embodiments, the determining portion 2121 is further configured to determine a predictive transform enable flag corresponding to the point cloud; the predictive transform enable flag indicates whether a predictive transform coding mode is enabled for a RAHT transform layer in the point cloud; and / or determine the number of coding mode flags corresponding to the point cloud;

[0478] The generating part 213 is further configured to write at least one of the prediction enable transformation flag and the number of the coding mode flags into the bitstream.

[0479] In some embodiments, the encoding part 211 is further configured to divide the nodes in the current layer into at least two node groups;

[0480] For each node group of the at least two node groups, at least one coding cost corresponding to each node in each node group is determined; a RAHT coding mode corresponding to each node group is determined based on the at least one coding cost corresponding to each node group; attribute coding information corresponding to each node in each node group is determined based on the RAHT coding mode corresponding to each node group, thereby determining the attribute coding information corresponding to each node group; and at least two sets of attribute coding information corresponding to the current layer and a RAHT coding mode corresponding to each set of attribute coding information are determined based on the RAHT coding mode corresponding to each node group and the attribute coding information corresponding to each node group, and a codestream is generated.

[0481] It is understood that in this embodiment, a "unit" can be a portion of a circuit, a portion of a processor, a portion of a program or software, etc., and can also be a module or a non-modular system. Furthermore, the various components in this embodiment can be integrated into a single processing unit, or each unit can exist physically separately, or two or more units can be integrated into a single unit. The aforementioned integrated units can be implemented in the form of hardware or software functional modules.

[0482] It should be noted that the description of the above encoder device embodiment is similar to the description of the above encoding method embodiment, and has similar beneficial effects as the method embodiment. For technical details not disclosed in the device embodiment of the present invention, please refer to the description of the method embodiment of the present invention for understanding.

[0483] If the integrated unit is implemented as a software functional module and is not sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this embodiment, or the portion that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, server, or network device, etc.) or a processor to execute all or part of the steps of the method described in this embodiment. The aforementioned storage medium includes various media that can store program code, such as a USB flash drive, a mobile hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0484] Therefore, an embodiment of the present application provides a storage medium (i.e., a computer-readable storage medium), which is applied to the encoder 20. The computer-readable storage medium stores a computer program, and when the computer program is executed by the first processor, it implements the method described in any one of the aforementioned embodiments.

[0485] Based on the composition of the above-mentioned encoder 20 and the computer-readable storage medium, Figure 44 is a second schematic diagram of the composition structure of the encoder. As shown in Figure 44, the encoder 20 may include: a first memory 221 and a first processor 222, a first communication interface 223 and a first bus system 224. The first memory 221, the first processor 222, and the first communication interface 223 are coupled together through the first bus system 224. It can be understood that the first bus system 224 is used to achieve connection and communication between these components. In addition to the data bus, the first bus system 224 also includes a power bus, a control bus, and a status signal bus. However, for the sake of clarity, all buses are labeled as the first bus system 224. Among them,

[0486] The first communication interface 223 is used to receive and send signals during the process of sending and receiving information between other external network elements;

[0487] The first memory 221 is used to store computer programs that can be run on the first processor;

[0488] The first processor 222 is used to determine the first node number of the nodes of the current layer and the second node number of the child nodes corresponding to the nodes of the current layer; wherein the first node number and the second node number are used to determine whether to perform RAHT transformation on the nodes of the current layer; based on the first node number and the second node number, determine the attribute reconstruction value of the child node corresponding to the node of the current layer.

[0489] It is understood that the first memory 221 in the embodiment of the present application can be a volatile memory or a non-volatile memory, or can include both volatile and non-volatile memories. Among them, the non-volatile memory can be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory can be a random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of RAM are available, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDRSDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link dynamic random access memory (SLDRAM), and direct RAM bus random access memory (DRRAM). The first memory 221 of the systems and methods described herein is intended to include, but is not limited to, these and any other suitable types of memory.

[0490] The first processor 222 may be an integrated circuit chip with signal processing capabilities. During implementation, each step of the above method can be completed by hardware integrated logic circuits or software instructions in the first processor 222. The above-mentioned first processor 222 may be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. The various methods, steps, and logic block diagrams disclosed in the embodiments of this application can be implemented or executed. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in the embodiments of this application can be directly implemented and executed by a hardware decoding processor, or by a combination of hardware and software modules in the decoding processor. The software module can be located in a storage medium mature in the art, such as random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, etc. The storage medium is located in the first memory 221 , and the first processor 222 reads the information in the first memory 221 and completes the steps of the above method in combination with its hardware.

[0491] It is to be understood that these embodiments described in the present application can be implemented with hardware, software, firmware, middleware, microcode or its combination.For hardware implementation, the processing unit can be implemented in one or more application specific integrated circuits (Application Specific Integrated Circuits, ASIC), digital signal processor (Digital Signal Processing, DSP), digital signal processing equipment (DSP Device, DSPD), programmable logic device (Programmable Logic Device, PLD), field programmable gate array (Field-Programmable Gate Array, FPGA), general-purpose processor, controller, microcontroller, microprocessor, other electronic units for performing functions described in the present application or its combination.For software implementation, the technology described in the present application can be realized by the module (such as process, function etc.) that performs functions described in the present application. The software code can be stored in a memory and executed by a processor. The memory can be implemented in the processor or outside the processor.

[0492] Optionally, as another embodiment, the first processor 222 is further configured to execute the method described in any one of the aforementioned embodiments when running the computer program.

[0493] FIG45 is a schematic diagram of the structure of a decoder. As shown in FIG45 , the decoder 30 may include:

[0494] a parsing portion 311 configured to parse a bitstream and determine a RAHT coding mode corresponding to a current layer and attribute coding information corresponding to a node in the current layer; the RAHT coding mode corresponding to the current layer is determined by encoding the attribute information of the node in the current layer by an encoder using at least one region adaptive layered transform (RAHT) coding mode, and determining at least one coding cost corresponding to the node based on the at least one coding cost corresponding to the node;

[0495] The decoding and reconstruction part 312 is configured to decode and reconstruct the attribute coding information corresponding to the node in the current layer based on the RAHT coding mode corresponding to the current layer, and determine the reconstructed attribute information corresponding to the node. It can be understood that in this embodiment, the "unit" can be part of the circuit, part of the processor, part of the program or software, etc., and of course it can also be a module or non-modular. Moreover, the various components in this embodiment can be integrated into a processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of a software functional module.

[0496] In some embodiments, the decoding and reconstruction part 312 is further configured to perform RAHT transform decoding on the attribute coding information to determine the reconstructed attribute information corresponding to the node when the RAHT coding mode is a RAHT transform coding mode; wherein the RAHT transform coding mode represents that the encoder performs RAHT transform and encoding on the attribute information of the node.

[0497] In some embodiments, the decoding and reconstruction part 312 is further configured to predict the attribute transformation information corresponding to the node in the current layer when the RAHT coding mode is the RAHT prediction transform coding mode, and determine the attribute information prediction value corresponding to the node in the current layer; based on the attribute information prediction value, perform RAHT transform decoding on the attribute coding information to determine the reconstructed attribute information corresponding to the node in the current layer; wherein the RAHT prediction transform coding representation encoder performs RAHT transform on the attribute information of the node, and predictively encodes the attribute transformation information determined by the RAHT transform.

[0498] In some embodiments, the RAHT prediction transform coding mode includes: a RAHT intra-frame prediction transform coding mode; the decoding and reconstruction part 312 is also configured to determine the attribute information prediction value corresponding to the node in the current layer based on the attribute information prediction value corresponding to the neighboring node of the node in the current layer when the RAHT coding mode is an intra-frame prediction transform coding mode.

[0499] In some embodiments, the RAHT prediction transform coding mode includes: a RAHT inter-frame prediction transform coding mode, and the decoding and reconstruction part 312 is further configured to determine the co-located node corresponding to the position of the node in the current layer in the reference point cloud when the RAHT coding mode is an inter-frame prediction transform coding mode; and determine the attribute information prediction value corresponding to the node in the current layer based on the reconstructed attribute transformation information of the co-located node.

[0500] In some embodiments, the decoding and reconstruction part 312 is further configured to determine the attribute information prediction value corresponding to the node in the current layer based on the attribute information prediction value corresponding to the neighboring node of the node in the current layer in the absence of the co-located node.

[0501] In some embodiments, the parsing part 311 is further configured to determine the RAHT coding mode corresponding to the current layer based on the RAHT coding mode flag corresponding to the current layer; wherein the RAHT coding mode flag is used to represent the RAHT transform coding mode or the RAHT prediction transform coding mode; the RAHT prediction transform coding mode includes: inter-frame prediction transform coding mode or intra-frame prediction transform coding mode.

[0502] In some embodiments, the parsing part 311 is further configured to determine the number of coding mode flags corresponding to the point cloud; the point cloud is the point cloud where the current layer is located; according to the number of the coding mode flags, the RAHT coding mode flag in the code stream is parsed to determine the RAHT coding mode flag corresponding to each layer in the point cloud.

[0503] In some embodiments, the decoding and reconstruction part 312 is further configured to determine, by parsing the code stream, at least two groups of attribute coding information corresponding to the current layer, and a RAHT coding mode corresponding to each group of attribute coding information in the at least two groups of attribute coding information; the at least two groups of attribute coding information correspond to at least two node groups; the at least two node groups are obtained by dividing the nodes in the current layer; the RAHT coding mode corresponding to each group of attribute coding information is determined based on at least one coding cost corresponding to each node group; the at least one coding cost is a coding cost corresponding to at least one RAHT coding mode; according to the RAHT coding mode corresponding to each group of attribute coding information, each group of attribute coding information is decoded and reconstructed to determine the reconstructed attribute information corresponding to each group of attribute coding information, thereby determining the reconstructed attribute information corresponding to the node in the current layer.

[0504] In some embodiments, the parsing part 311 is further configured to determine the prediction transform enable flag corresponding to the point cloud by parsing the code stream; the prediction transform enable flag represents whether the prediction transform coding mode is enabled for the point cloud; when the prediction transform enable flag represents the enabling of the prediction transform coding mode, determine the number of coding mode flags corresponding to the point cloud.

[0505] In some embodiments, the decoding and reconstruction part 312 is also configured to determine whether the number of neighboring nodes of the parent node of each node in the current layer is greater than a preset first number threshold; if it is greater than the preset first number threshold, determine whether the number of neighboring nodes of each node in the current layer is greater than a preset second number threshold; if it is greater than the preset second number threshold, determine the decoding mode corresponding to each node in the current layer according to the RAHT coding mode corresponding to the current layer.

[0506] It should be noted that the description of the above encoder device embodiment is similar to the description of the above encoding method embodiment, and has similar beneficial effects as the method embodiment. For technical details not disclosed in the device embodiment of the present invention, please refer to the description of the method embodiment of the present invention for understanding.

[0507] If the integrated unit is implemented as a software functional module and is not sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this embodiment, or the portion that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, server, or network device, etc.) or a processor to execute all or part of the steps of the method described in this embodiment. The aforementioned storage medium includes various media that can store program code, such as a USB flash drive, a mobile hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0508] Therefore, an embodiment of the present application provides a storage medium, namely a computer-readable storage medium, applied to the decoder 30, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by the first processor, the method described in any one of the aforementioned embodiments is implemented.

[0509] Based on the composition of the above-mentioned decoder 30 and the computer-readable storage medium, Figure 46 is a second schematic diagram of the composition structure of the decoder. As shown in Figure 46, the decoder 30 may include: a second memory 321 and a second processor 322, a second communication interface 323 and a second bus system 324. The second memory 321 and the second processor 322, and the second communication interface 323 are coupled together through the second bus system 324. It can be understood that the second bus system 324 is used to realize the connection and communication between these components. In addition to the data bus, the second bus system 324 also includes a power bus, a control bus and a status signal bus. However, for the sake of clarity, various buses are labeled as the second bus system 324. Among them,

[0510] The second communication interface 323 is used to receive and send signals during the process of sending and receiving information between other external network elements;

[0511] The second memory 321 is used to store computer programs that can be run on the second processor;

[0512] The second processor 322 is used to determine the first node number of the nodes of the current layer and the second node number of the child nodes corresponding to the nodes of the current layer; wherein the first node number and the second node number are used to determine whether to perform RAHT transformation on the nodes of the current layer; and determine the attribute reconstruction value of the child node corresponding to the node of the current layer based on the first node number and the second node number.

[0513] It is understood that the second memory 321 in the embodiment of the present application can be a volatile memory or a non-volatile memory, or can include both volatile and non-volatile memories. Among them, the non-volatile memory can be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory can be a random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of RAM are available, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDRSDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link dynamic random access memory (SLDRAM), and direct RAM bus random access memory (DRRAM). The second memory 321 of the systems and methods described herein is intended to include, but is not limited to, these and any other suitable types of memory.

[0514] The second processor 322 may be an integrated circuit chip with signal processing capabilities. During implementation, each step of the above method can be completed by hardware integrated logic circuits or software instructions in the second processor 322. The above-mentioned second processor 322 can be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. It can implement or execute the various methods, steps, and logic block diagrams disclosed in the embodiments of this application. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in the embodiments of this application can be directly implemented and executed by a hardware decoding processor, or by a combination of hardware and software modules in the decoding processor. The software module can be located in a storage medium mature in the art, such as random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, etc. The storage medium is located in the second memory 321 , and the second processor 322 reads the information in the second memory 321 and completes the steps of the above method in combination with its hardware.

[0515] It is to be understood that these embodiments described in the present application can be implemented with hardware, software, firmware, middleware, microcode or its combination.For hardware implementation, the processing unit can be implemented in one or more application specific integrated circuits (Application Specific Integrated Circuits, ASIC), digital signal processor (Digital Signal Processing, DSP), digital signal processing equipment (DSP Device, DSPD), programmable logic device (Programmable Logic Device, PLD), field programmable gate array (Field-Programmable Gate Array, FPGA), general-purpose processor, controller, microcontroller, microprocessor, other electronic units for performing functions described in the present application or its combination.For software implementation, the technology described in the present application can be realized by the module (such as process, function etc.) that performs functions described in the present application. The software code can be stored in a memory and executed by a processor. The memory can be implemented in the processor or outside the processor.

[0516] In yet another embodiment of the present application, see Figure 47 , which shows a schematic diagram of the composition structure of a coding and decoding system provided by an embodiment of the present application. As shown in Figure 47 , the coding and decoding system 230 may include an encoder 2301 and a decoder 2302 .

[0517] In the embodiment of the present application, the encoder 2301 may be the encoder described in any one of the aforementioned embodiments, and the decoder 2302 may be the decoder described in any one of the aforementioned embodiments.

[0518] In another embodiment of the present application, the embodiment of the present application further provides a code stream, which is generated by bit encoding based on information to be encoded; wherein the information to be encoded includes at least: a RAHT coding mode corresponding to a current layer and attribute coding information corresponding to a node in the current layer; the RAHT coding mode corresponding to the current layer is determined based on at least one coding cost corresponding to the node in the current layer; and the at least one coding cost corresponding to the node in the current layer is determined by encoding the attribute information of the node in the current layer through at least one RAHT coding mode.

[0519] It should be noted that, in the embodiments of the present application, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0520] The serial numbers of the above-mentioned embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0521] The methods disclosed in the several method embodiments provided in this application can be arbitrarily combined without conflict to obtain new method embodiments.

[0522] The features disclosed in the several product embodiments provided in this application can be arbitrarily combined without conflict to obtain new product embodiments.

[0523] The features disclosed in the several method or device embodiments provided in this application can be arbitrarily combined without conflict to obtain new method embodiments or device embodiments.

[0524] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims. Industrial Applicability

[0525] The embodiment of the present application provides a point cloud encoding and decoding method, encoder, decoder, code stream and storage medium. The encoder encodes each node in the current layer through at least one RAHT encoding method, determines at least one encoding cost and at least one candidate attribute encoding information corresponding to each node, and thus can determine the best encoding mode for the current layer based on the at least one encoding cost corresponding to each node, and use the encoding mode to determine the attribute encoding information corresponding to each node in the current layer, and transmit the RAHT encoding mode corresponding to the current layer and the attribute encoding information corresponding to the node to the decoding end. The decoder decodes and reconstructs the attribute encoding information corresponding to the node in the current layer according to the RAHT encoding mode transmitted by the encoder, and determines the reconstructed attribute information corresponding to the node. In this way, by introducing multiple encoding modes and combining the encoding cost to adaptively select the best encoding and decoding mode, the attribute distribution characteristics and spatial distribution characteristics of each node are comprehensively considered, the RAHT attribute encoding and decoding efficiency and the encoding and decoding efficiency of the point cloud attribute information are improved, and the point cloud encoding and decoding performance is thereby improved.

Claims

1. A point cloud decoding method, applied to a decoder, the method comprising: Parse the bitstream to determine the RAHT coding mode corresponding to the current layer and the attribute coding information corresponding to the nodes in the current layer; The RAHT coding mode corresponding to the current layer is that the encoder encodes the attribute information of the node of the current layer through at least one regional adaptive hierarchical transform RAHT coding mode, determines at least one coding cost corresponding to the node, and is determined based on the at least one coding cost corresponding to the node; Based on the RAHT coding mode corresponding to the current layer, attribute coding information corresponding to the nodes in the current layer is decoded and reconstructed to determine the reconstructed attribute information corresponding to the nodes.

2. The method according to claim 1, wherein: The decoding and reconstructing the attribute coding information corresponding to the node in the current layer based on the RAHT coding mode corresponding to the current layer to determine the reconstructed attribute information corresponding to the node includes: When the RAHT coding mode is a RAHT transform coding mode, performing RAHT transform decoding on the attribute coding information to determine the reconstructed attribute information corresponding to the node; The RAHT transform coding mode represents that the encoder performs RAHT transform and coding on the attribute information of the node.

3. The method according to claim 1, wherein: The decoding and reconstructing the attribute coding information corresponding to the node in the current layer based on the RAHT coding mode corresponding to the current layer to determine the reconstructed attribute information corresponding to the node includes: When the RAHT coding mode is the RAHT prediction transform coding mode, predicting the attribute transform information corresponding to the node in the current layer, and determining the predicted value of the attribute information corresponding to the node in the current layer; Based on the predicted value of the attribute information, the attribute encoding information is decoded by RAHT transform to determine the reconstructed attribute information corresponding to the node in the current layer; The RAHT prediction transformation coding representation encoder performs RAHT transformation on the attribute information of the node, and performs prediction coding on the attribute transformation information determined by the RAHT transformation.

4. The method according to claim 3, wherein: The RAHT prediction transform coding mode includes: a RAHT intra-frame prediction transform coding mode; when the RAHT coding mode is the RAHT prediction transform coding mode, predicting the attribute transform information corresponding to the node in the current layer, and determining the predicted value of the attribute information corresponding to the node in the current layer, includes: In the case where the RAHT coding mode is an intra-frame prediction transform coding mode, the attribute information prediction value corresponding to the node in the current layer is determined according to the attribute information prediction value corresponding to the neighboring node of the node in the current layer.

5. The method according to claim 3, wherein: The RAHT prediction transform coding mode includes: a RAHT inter-frame prediction transform coding mode, and when the RAHT coding mode is the RAHT prediction transform coding mode, predicting the attribute transform information corresponding to the node in the current layer, and determining the predicted value of the attribute information corresponding to the node in the current layer, includes: In a case where the RAHT coding mode is an inter-frame prediction transform coding mode, determining a co-located node corresponding to a position of the node in the current layer in the reference point cloud; Based on the reconstructed attribute transformation information of the co-located node, a predicted value of the attribute information corresponding to the node in the current layer is determined.

6. The method according to claim 5, wherein: The method further comprises: In the absence of the co-located node, the predicted attribute information value corresponding to the node in the current layer is determined based on the predicted attribute information value corresponding to the neighboring node of the node in the current layer.

7. The method according to any one of claims 1 to 6, wherein: The determining the RAHT coding mode corresponding to the current layer includes: According to the RAHT coding mode flag bit corresponding to the current layer, the RAHT coding mode corresponding to the current layer is determined; wherein, The RAHT coding mode flag is used to represent a RAHT transform coding mode or a RAHT prediction transform coding mode; the RAHT prediction transform coding mode includes: an inter-frame prediction transform coding mode or an intra-frame prediction transform coding mode.

8. The method according to claim 7, wherein: The method further comprises: Determine the number of coding mode flag bits corresponding to a point cloud; the point cloud is the point cloud where the current layer is located; According to the number of the coding mode flags, the RAHT coding mode flags in the bitstream are parsed to determine the RAHT coding mode flags corresponding to each layer in the point cloud.

9. The method according to claim 1, wherein: The method further comprises: By parsing the bitstream, at least two groups of attribute coding information corresponding to the current layer and a RAHT coding mode corresponding to each group of attribute coding information in the at least two groups of attribute coding information are determined; the at least two groups of attribute coding information correspond to at least two node groups; the at least two node groups are obtained by dividing the nodes in the current layer; the RAHT coding mode corresponding to each group of attribute coding information is determined based on at least one coding cost corresponding to each node group; the at least one coding cost is a coding cost corresponding to at least one RAHT coding mode; According to the RAHT coding mode corresponding to each set of attribute coding information, each set of attribute coding information is decoded and reconstructed to determine The reconstructed attribute information corresponding to each set of attribute coding information is determined, thereby determining the reconstructed attribute information corresponding to the node in the current layer.

10. The method according to claim 8, wherein: The method further comprises: Determine, by parsing the bitstream, a predictive transform enable flag corresponding to the point cloud; the predictive transform enable flag indicates whether a predictive transform coding mode is enabled for the point cloud; In a case where the prediction transform enable flag represents enabling the prediction transform coding mode, the number of coding mode flags corresponding to the point cloud is determined.

11. The method according to claim 7, wherein: The method further comprises: Determine whether the number of neighboring nodes of the parent node of each node in the current layer is greater than a preset first number threshold; In the case where the number of neighboring nodes of each node in the current layer is greater than the preset first number threshold, determining whether the number of neighboring nodes of each node in the current layer is greater than the preset second number threshold; When the number is greater than the preset second quantity threshold, a decoding mode corresponding to each node in the current layer is determined according to the RAHT coding mode corresponding to the current layer.

12. A point cloud encoding method, applied to an encoder, the method comprising: Encoding attribute information of a node in a current layer by using at least one regional adaptive hierarchical transform (RAHT) coding mode, and determining at least one coding cost and at least one candidate attribute coding information corresponding to the node; Determine, based on at least one coding cost corresponding to the node, a RAHT coding mode corresponding to the current layer, and determine attribute coding information corresponding to the node from the at least one candidate attribute coding information; A code stream is generated based on the RAHT coding mode corresponding to the current layer and the attribute coding information corresponding to the node.

13. The method according to claim 12, wherein: The at least one candidate attribute coding information includes: transform coding information and prediction transform coding information; encoding the attribute information of the node in the current layer by at least one regional adaptive hierarchical transform (RAHT) coding mode, and determining at least one coding cost and at least one candidate attribute coding information corresponding to the node, including: Determine attribute transformation information and transformation coding information corresponding to each node in the current layer by performing RAHT transformation coding on the attribute information of each node in the point cloud; Performing predictive coding on the attribute transformation information corresponding to each node in the current layer to determine the predictive transformation coding information corresponding to each node in the current layer; At least one coding cost corresponding to the node is determined based on the transform coding information and the prediction transform coding information.

14. The method according to claim 13, wherein: The predictive coding of the attribute transformation information corresponding to each node in the current layer to determine the predictive transformation coding information corresponding to each node in the current layer includes: Determine whether the number of neighboring nodes of the parent node of each node in the current layer is greater than a preset first number threshold; In the case where the number of neighboring nodes of each node in the current layer is greater than the preset first number threshold, determining whether the number of neighboring nodes of each node in the current layer is greater than the preset second number threshold; When the number is greater than the preset second quantity threshold, prediction coding is performed on the attribute transformation information corresponding to each node in the current layer to determine the prediction transformation coding information corresponding to each node in the current layer.

15. The method according to claim 13 or 14, wherein: The step of performing RAHT transform encoding on the attribute information of each node in the point cloud to determine the attribute transform information and transform encoding information corresponding to each node in the current layer includes: Based on the RAHT attribute transformation coding structure corresponding to the point cloud, starting from the voxel-level nodes, the attribute information of each node in the point cloud is recursively transformed and encoded until the root node, and the attribute transformation information and transformation coding information corresponding to each node in the point cloud are determined, so as to determine the transformation coding information corresponding to each node in the current layer; the attribute transformation information is determined by performing a RAHT transformation on the attribute information; and the transformation coding information is determined by encoding the attribute transformation information.

16. The method according to claim 13 or 14, wherein: The prediction transformation coding information includes: inter-frame prediction transformation coding information; the prediction coding of the attribute transformation information corresponding to each node in the current layer to determine the prediction transformation coding information corresponding to each node in the current layer includes: Inter-frame prediction coding is performed on the attribute transformation information corresponding to each node in the current layer to determine the inter-frame prediction transformation coding information corresponding to each node in the current layer.

17. The method according to claim 13 or 14, wherein: The prediction transformation coding information includes: intra-frame prediction transformation coding information; predictive coding is performed on the attribute transformation information corresponding to each node in the current layer, and the prediction transformation coding information corresponding to each node in the current layer is determined, including: Intra-frame prediction coding is performed on the attribute transformation information corresponding to each node in the current layer to determine the intra-frame prediction transformation coding information corresponding to each node in the current layer.

18. The method according to claim 13 or 14, wherein: The step of performing RAHT transform encoding on the attribute information of each node in the point cloud to determine the attribute transform information and transform encoding information corresponding to each node in the current layer includes: Based on the RAHT attribute transformation coding structure corresponding to the point cloud, starting from the root node, determine the N corresponding to each node in the point cloud Child nodes; For the N child nodes corresponding to each node, perform RAHT attribute transformation and encoding on the attribute information of the N child nodes, determine the attribute transformation information and transformation encoding information corresponding to the N child nodes, and thus determine the attribute transformation information and transformation encoding information corresponding to each node in the point cloud; N is greater than 0 and not greater than a preset child node number threshold; According to the attribute transformation information and transformation coding information corresponding to each node in the point cloud, the attribute transformation information and transformation coding information corresponding to each node in the current layer are determined.

19. The method according to claim 16, wherein: The performing inter-frame prediction coding on the attribute transformation coefficient corresponding to each node in the current layer to determine the inter-frame prediction transformation coding information corresponding to each node in the current layer includes: Determine a co-located node corresponding to a position of each node in the current layer in a reference point cloud corresponding to the point cloud; Determine a predicted value of attribute information corresponding to each node in the current layer based on the reconstructed attribute transformation information of the co-located node; Based on the attribute information prediction value, the attribute transformation information corresponding to each node in the current layer is encoded, and the inter-frame prediction transformation coding information corresponding to each node in the current layer is determined.

20. The method according to claim 16, wherein: The performing inter-frame prediction coding on the attribute transformation information corresponding to each node in the current layer to determine the inter-frame prediction transformation coding information corresponding to each node in the current layer includes: Determine a corresponding co-located node for each node in the current layer in a reference point cloud corresponding to the point cloud; In the case where each node in the current layer is a parent node in the current layer, determining a predicted value of attribute information corresponding to each node in the current layer based on the reconstructed attribute transformation information of the co-located node; In the case where each node in the current layer is a child node in the current layer, determining a predicted value of attribute information corresponding to each node in the current layer based on reconstructed attribute transformation information of M child nodes corresponding to the co-located node in the reference point cloud; M is greater than 0 and not greater than a preset child node number threshold; Based on the attribute information prediction value, the attribute transformation information corresponding to each node in the current layer is encoded, and the inter-frame prediction transformation coding information corresponding to each node in the current layer is determined.

21. The method according to claim 20, wherein: Each node in the current layer includes: a child node in the current layer; and determining the attribute information prediction value corresponding to each node in the current layer based on the reconstructed attribute transformation information of the M child nodes corresponding to the co-located node in the reference point cloud, including: Determine the co-located child node corresponding to the position of each child node in the M child nodes; In a case where the reconstructed attribute transformation information of the co-located child node is greater than a preset information value threshold, determining the attribute information prediction value of each node in the current layer according to the reconstructed attribute transformation information of the co-located child node; When the reconstructed attribute transformation information of the co-located child node is less than or equal to the preset information value threshold, the attribute information prediction value corresponding to each child node is determined based on the reconstructed attribute transformation information of the neighboring nodes of each child node.

22. The method according to any one of claims 19 to 21, wherein: The method further comprises: When there is no co-located node with a corresponding position for each node in the current layer in the reference point cloud corresponding to the point cloud, the attribute information prediction value corresponding to each node in the current layer is determined based on the attribute information prediction value of the neighboring nodes of each node in the current layer.

23. The method according to any one of claims 13, 14, 19-21, wherein: The prediction transform coding information includes: intra-frame prediction transform coding information and inter-frame prediction transform coding information; the at least one coding cost includes: a first rate-distortion cost, a second rate-distortion cost, and a third rate-distortion cost; and determining at least one coding cost corresponding to each node in the current layer based on the transform coding information and the prediction transform coding information includes: Decoding and reconstructing based on the transform coding information to determine a first rate-distortion cost corresponding to each node in the current layer; Decoding and reconstructing based on the intra-frame prediction transform coding information to determine a second rate-distortion cost corresponding to each node in the current layer; Decoding and reconstruction are performed based on the inter-frame prediction transform coding information to determine a third rate-distortion cost corresponding to each node in the current layer.

24. The method according to claim 23, wherein: The determining, based on at least one coding cost corresponding to the node, a RAHT coding mode corresponding to the current layer includes: Determining a first coding cost corresponding to the current layer based on a first rate-distortion cost corresponding to each node in the current layer; the first coding cost corresponds to a RAHT transform coding mode; Determining a second coding cost corresponding to the current layer based on a second rate-distortion cost corresponding to each node in the current layer; the second coding cost corresponds to a RAHT intra-frame prediction transform coding mode; Determining a third coding cost corresponding to the current layer based on a third rate-distortion cost corresponding to each node in the current layer; the third coding cost corresponds to a RAHT inter-frame prediction transform coding mode; By comparing the first coding cost, the first coding cost, and the third coding cost, determining the current layer corresponding to RAHT encoding mode.

25. The method of claim 12, wherein: The method further comprises: Determine a RAHT coding mode corresponding to the current layer based on attribute information of a parent node of the node of the current layer and reconstruction attribute information of neighboring nodes of the parent node; The attribute information of the nodes in the current layer is encoded using the RAHT coding mode corresponding to the current layer to determine the attribute coding information corresponding to the nodes.

26. The method according to claim 25, wherein: The determining, based on the attribute information of the parent node of the node of the current layer and the reconstruction attribute information of the neighboring nodes of the parent node, the RAHT coding mode corresponding to the current layer includes: When an error between the attribute information of the parent node of the node in the current layer and the reconstructed attribute information of the neighboring node of the parent node is greater than a preset error threshold; determining the RAHT transform coding mode as the RAHT coding mode corresponding to the current layer; the transform coding mode represents RAHT transform and coding of the attribute information; When the error between the attribute information of the parent node of the node in the current layer and the reconstructed attribute information of the neighboring nodes of the parent node is less than or equal to the preset error threshold, the RAHT prediction transform coding mode is determined as the RAHT coding mode corresponding to the current layer; the prediction transform coding mode represents the prediction coding of the attribute transform coefficients determined by the RAHT transform of the attribute information.

27. The method according to any one of claims 12-14, 19-21, 24-26, wherein: The generating a bitstream based on the RAHT coding mode corresponding to the current layer and the attribute coding information corresponding to the node includes: According to the RAHT coding mode corresponding to the current layer, determining the RAHT coding mode flag corresponding to the current layer; the RAHT coding mode flag is used to represent the RAHT transform coding mode or the RAHT prediction transform coding mode; the RAHT prediction transform coding mode includes: an inter-frame prediction transform coding mode or an intra-frame prediction transform coding mode; Determine the attribute coding information corresponding to the current layer based on the attribute coding information corresponding to the node; Determine, by processing each RAHT transformation layer in the point cloud, a coding mode flag corresponding to each RAHT transformation layer and attribute coding information corresponding to each RAHT transformation layer; The code stream is generated based on the coding mode flag corresponding to each RAHT transformation layer and the attribute coding information corresponding to each RAHT transformation layer.

28. The method according to claim 27, wherein: The method further comprises: Based on the RAHT attribute transform coding structure, downsampling is performed starting from a root node along each spatial coordinate axis direction to determine at least one RAHT transform layer corresponding to the point cloud; the at least one RAHT transform layer includes the current layer.

29. The method according to claim 27, wherein: The method further comprises: Determining a prediction transform enable flag corresponding to the point cloud; the prediction transform enable flag indicates whether a prediction transform coding mode is enabled for a RAHT transform layer in the point cloud; and / or, Determine the number of encoding mode flag bits corresponding to the point cloud; At least one of the prediction enable transformation flag and the number of the coding mode flag is written into the bitstream.

30. The method according to any one of claims 12-14, 19-21, 24-26, 28, 29, wherein The method further comprises: Dividing the nodes in the current layer into at least two node groups; For each node group of the at least two node groups, determining at least one encoding cost corresponding to each node group based on at least one encoding cost corresponding to each node in the each node group; Determine, based on at least one coding cost corresponding to each node group, a RAHT coding mode corresponding to each node group; Determine attribute coding information corresponding to each node in each node group based on the RAHT coding mode corresponding to each node group, thereby determining the attribute coding information corresponding to each node group; According to the RAHT coding mode corresponding to each node group and the attribute coding information corresponding to each node group, at least two groups of attribute coding information corresponding to the current layer and the RAHT coding mode corresponding to each group of attribute coding information are determined, and a code stream is generated.

31. A decoder comprising: A parsing part, configured to parse the bitstream, determine the RAHT coding mode corresponding to the current layer and the attribute coding information corresponding to the node in the current layer; The RAHT coding mode corresponding to the current layer is that the encoder encodes the attribute information of the node of the current layer through at least one regional adaptive hierarchical transform RAHT coding mode, determines at least one coding cost corresponding to the node, and is determined based on the at least one coding cost corresponding to the node; The decoding and reconstruction part is configured to decode and reconstruct the attribute coding information corresponding to the node in the current layer based on the RAHT coding mode corresponding to the current layer, and determine the reconstructed attribute information corresponding to the node.

32. An encoder comprising: The encoding part is configured to encode the attribute information of the node in the current layer through at least one regional adaptive hierarchical transform (RAHT) encoding mode, and determine at least one encoding cost and at least one candidate attribute encoding information corresponding to the node; The determining part is configured to determine the RAHT coding corresponding to the current layer based on at least one coding cost corresponding to the node mode, and determining the attribute coding information corresponding to the node from at least one candidate attribute coding information; The generating part is configured to generate a code stream based on the RAHT coding mode corresponding to the current layer and the attribute coding information corresponding to the node.

33. An encoder, comprising a first memory and a first processor; wherein: The first memory is used to store a computer program that can be run on the first processor; The first processor is configured to execute the method according to any one of claims 12 to 30 when running the computer program.

34. A decoder, comprising a second memory and a second processor; wherein: The second memory is used to store a computer program that can be run on the second processor; The second processor is configured to execute the method according to any one of claims 1 to 11 when running the computer program.

35. A code stream, the code stream is generated by bit encoding according to information to be encoded; wherein, The information to be encoded includes at least: the RAHT coding mode corresponding to the current layer and the attribute coding information corresponding to the nodes in the current layer; the RAHT coding mode corresponding to the current layer is determined based on at least one coding cost corresponding to the nodes in the current layer; and the at least one coding cost corresponding to the nodes in the current layer is determined by encoding the attribute information of the nodes in the current layer through at least one RAHT coding mode.

36. A storage medium, wherein: The storage medium stores a computer program, and when the computer program is executed, the method according to any one of claims 1 to 11 is implemented, or the method according to any one of claims 12 to 30 is implemented.

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