Encoding method and apparatus, decoding method and apparatus, point cloud encoder, point cloud decoder, bitstream, device, and storage medium

Abstract

An encoding method and apparatus, a decoding method and apparatus, a point cloud encoder, a point cloud decoder, a bitstream, a device, and a storage medium. The decoding method comprises: when a current transform layer is an upper layer of a current point cloud, determining a prediction mode of a current transform block of the current transform layer on the basis of a predefined first-layer prediction mode of the upper layer, wherein the first-layer prediction mode comprises one or more prediction modes; determining a predicted value of attribute information of the current transform block on the basis of the prediction mode of the current transform block; and determining the attribute information of the current transform block on the basis of the predicted value of the attribute information of the current transform block.

Description

Encoding and decoding methods and apparatus, point cloud codecs, bitstreams, devices, and storage media Technical Field

[0001] This application relates to point cloud compression technology, including but not limited to encoding and decoding methods and apparatus, point cloud codecs, bitstreams, devices, and storage media. Background Technology

[0002] A point cloud is a set of randomly distributed discrete points in space that represent the spatial structure and surface properties of a three-dimensional object or scene. Point cloud data typically includes geometric and attribute information of the sampling points; the geometric information includes the three-dimensional position information (x, y, z) of the sampling points, and the attribute information includes the color information and / or one-dimensional reflectance information of the sampling points, etc.

[0003] Point clouds can flexibly and conveniently represent the spatial structure and surface properties of 3D objects or scenes. Because point clouds are obtained by directly sampling real objects, they can provide a strong sense of realism while maintaining accuracy, thus leading to their wide range of applications, including virtual reality games, computer-aided design, geographic information systems, automatic navigation systems, digital cultural heritage, free-viewpoint broadcasting, 3D immersive telepresence, and 3D reconstruction of biological tissues and organs. Therefore, improving the encoding and decoding efficiency of point clouds is of significant importance.

[0004] Summary of the Invention

[0005] The encoding and decoding methods, apparatus, point cloud codecs, bitstreams, devices, and storage media provided in this application are intended to reduce codeword overhead at the encoding end and improve encoding and decoding efficiency.

[0006] In a first aspect, embodiments of this application provide a decoding method applied to a point cloud decoder. The method includes: when the current transform layer is above the current point cloud, determining the prediction mode of the current transform block of the current transform layer according to a predefined first-layer prediction mode of the upper layer; the first-layer prediction mode includes one or more prediction modes; determining the predicted value of the attribute information of the current transform block according to the prediction mode of the current transform block; and determining the attribute information of the current transform block according to the predicted value of the attribute information of the current transform block.

[0007] It is understood that in the decoding method provided in this application embodiment, for the current transform layer that belongs to the upper layer of the current point cloud, its layer prediction mode is the predefined first layer prediction mode, rather than being parsed from the bitstream; thus, it saves bitstream overhead and is also beneficial to improving encoding and decoding efficiency.

[0008] Secondly, embodiments of this application provide a decoding method applied to a point cloud decoder. The method includes: when the current transform layer is a middle or upper layer of the current point cloud, decoding the bitstream and determining a first syntax element; determining a layer prediction mode of the current transform layer based on the first syntax element; wherein the layer prediction mode indicated by the first syntax element is either a second layer prediction mode or a third layer prediction mode; determining a prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer; determining a predicted value of the attribute information of the current transform block based on the prediction mode of the current transform block; and determining the attribute information of the current transform block based on the predicted value of the attribute information of the current transform block.

[0009] It is understood that in the decoding method provided in this application embodiment, for the current transform layer belonging to the middle and upper layers of the current point cloud, its layer prediction mode is indicated by the first syntax element. The first syntax element indicates any one of the second layer prediction mode and the third layer prediction mode. Therefore, the first syntax element can indicate the layer prediction mode of the middle and upper layers using only 1 bit, without needing to use two or more bits to indicate the layer prediction mode of the middle and upper layers; thus, it is beneficial to save bitstream overhead.

[0010] Thirdly, embodiments of this application provide a decoding method applied to a point cloud decoder. The method includes: when the current transform layer is the lowest layer of the current point cloud, determining the prediction mode of the current transform block of the current transform layer according to a predefined fourth-layer prediction mode of the lowest layer; the fourth-layer prediction mode includes one or more prediction modes; determining the predicted value of the attribute information of the current transform block according to the prediction mode of the current transform block; and determining the attribute information of the current transform block according to the predicted value of the attribute information of the current transform block.

[0011] It is understood that in the decoding method provided in this application embodiment, for the current transform layer which belongs to the lowest layer of the current point cloud, its layer prediction mode is the predefined fourth layer prediction mode, rather than being parsed from the bitstream; thus, it saves bitstream overhead and is also beneficial to improving encoding and decoding efficiency.

[0012] Fourthly, embodiments of this application provide an encoding method applied to a point cloud encoder. The method includes: when the current transform layer is above the current point cloud, determining the prediction mode of the current transform block of the current transform layer according to a predefined first-layer prediction mode of the upper layer; the first-layer prediction mode includes one or more prediction modes; determining the predicted value of the attribute information of the current transform block according to the prediction mode of the current transform block; obtaining the encoded bits according to the predicted value of the attribute information of the current transform block, and writing the encoded bits into the bit stream.

[0013] It is understood that, in the embodiments of this application, for the current transform layer that belongs to the upper layer of the current point cloud, its layer prediction mode is a predefined first layer prediction mode. The encoder can directly determine the prediction mode of the current transform block that belongs to the upper layer based on the first layer prediction mode, without the need for rate-distortion optimization. Thus, the layer prediction mode used by the decoder is determined from multiple layer prediction modes, and there is no need to indicate in the bitstream which layer prediction mode the upper layer current transform layer uses. In this way, the encoding efficiency is improved while saving bitstream overhead.

[0014] Fifthly, embodiments of this application provide an encoding method applied to a point cloud encoder. The method includes: when the current transform layer is a middle or upper layer of the current point cloud, determining a layer prediction mode of the current transform layer based on a second layer prediction mode and a third layer prediction mode; determining a prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer; determining predicted values ​​of attribute information of the current transform block based on the prediction mode of the current transform block; obtaining encoded bits based on the predicted values ​​of attribute information of the current transform block; and writing the encoded bits into the bitstream.

[0015] It is understood that in the encoding method provided in this application embodiment, for the current transform layer belonging to the middle and upper layers of the current point cloud, its layer prediction mode is determined based on the second layer prediction mode and the third layer prediction mode, rather than based on more layer prediction modes. Thus, at the encoding end, the encoder only needs to determine the rate-distortion cost corresponding to the second layer prediction mode and the third layer prediction mode corresponding to the current transform layer, without having to determine the rate-distortion cost of the third layer prediction mode. Therefore, the time overhead caused by calculating the rate-distortion cost is saved, thereby improving the encoding efficiency.

[0016] In a sixth aspect, embodiments of this application provide an encoding method applied to a point cloud encoder. The method includes: when the current transform layer is the lowest layer of the current point cloud, determining the prediction mode of the current transform block of the current transform layer according to a predefined fourth-layer prediction mode of the lowest layer; the fourth-layer prediction mode includes one or more prediction modes; determining the predicted value of the attribute information of the current transform block according to the prediction mode of the current transform block; obtaining the encoded bits according to the predicted value of the attribute information of the current transform block, and writing the encoded bits into the bit stream.

[0017] It is understood that, in the embodiments of this application, for the current transform layer that is the lowest layer of the current point cloud, its layer prediction mode is the predefined fourth layer prediction mode. The encoder can directly determine the prediction mode of the current transform block that belongs to the lowest layer of the current transform layer based on the fourth layer prediction mode, without the need for rate-distortion optimization. Thus, the layer prediction mode used by the decoder is determined from multiple layer prediction modes, and there is no need to indicate in the bitstream which layer prediction mode is used for the lowest layer of the current transform layer. In this way, the encoding efficiency is improved while saving bitstream overhead.

[0018] In a seventh aspect, embodiments of this application provide a decoding apparatus applied to a point cloud decoder. The apparatus includes: a first determining module configured to determine a prediction mode of a current transform block of the current transform layer based on a predefined first-layer prediction mode of the upper layer when the current transform layer is an upper layer of the current point cloud; the first-layer prediction mode includes one or more prediction modes; a second determining module configured to determine a predicted value of attribute information of the current transform block based on the prediction mode of the current transform block; and a third determining module configured to determine the attribute information of the current transform block based on the predicted value of the attribute information of the current transform block.

[0019] Eighthly, embodiments of this application provide a decoding apparatus applied to a point cloud decoder. The apparatus includes: a decoding module configured to decode a bitstream and determine a first syntax element when the current transform layer is a middle or upper layer of the current point cloud; a first determining module configured to determine a layer prediction mode of the current transform layer based on the first syntax element; and to determine a prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer; wherein the layer prediction mode indicated by the first syntax element is either a second layer prediction mode or a third layer prediction mode; a second determining module configured to determine a predicted value of attribute information of the current transform block based on the prediction mode of the current transform block; and a third determining module configured to determine the attribute information of the current transform block based on the predicted value of the attribute information of the current transform block.

[0020] Ninthly, embodiments of this application provide a decoding apparatus applied to a point cloud decoder. The apparatus includes: a first determining module configured to determine a prediction mode of a current transform block of the current transform layer based on a predefined fourth-layer prediction mode of the lowest layer when the current transform layer is the lowest layer of the current point cloud; the fourth-layer prediction mode includes one or more prediction modes; a second determining module configured to determine a predicted value of attribute information of the current transform block based on the prediction mode of the current transform block; and a third determining module configured to determine the attribute information of the current transform block based on the predicted value of the attribute information of the current transform block.

[0021] In a tenth aspect, embodiments of this application provide a point cloud decoder, including a first memory and a first processor; wherein the first memory is used to store a computer program that can run on the first processor; and the first processor is used to execute the decoding method of embodiments of this application when running the computer program.

[0022] Eleventhly, embodiments of this application provide a bitstream generated by the encoding method of embodiments of this application.

[0023] In a twelfth aspect, embodiments of this application provide an encoding apparatus applied to a point cloud encoder. The apparatus includes: a fourth determining module configured to determine a prediction mode of the current transform block of the current transform layer based on a predefined first-layer prediction mode of the upper layer when the current transform layer is an upper layer of the current point cloud; the first-layer prediction mode includes one or more prediction modes; a fifth determining module configured to determine a predicted value of the attribute information of the current transform block based on the prediction mode of the current transform block; and an encoding module configured to obtain encoded bits based on the predicted value of the attribute information of the current transform block and write the encoded bits into a bitstream.

[0024] In a thirteenth aspect, embodiments of this application provide an encoding apparatus applied to a point cloud encoder. The apparatus includes: a fourth determining module configured to determine the value of a first syntax element based on a second-layer prediction mode and a third-layer prediction mode when the current transform layer is a middle-upper layer of the current point cloud; the first syntax element is used to indicate that the layer prediction mode of the middle-upper layer is either the second-layer prediction mode or the third-layer prediction mode; the fourth determining module is configured to determine the prediction mode of the current transform block of the current transform layer based on the value of the first syntax element; a fifth determining module configured to determine the predicted value of the attribute information of the current transform block based on the prediction mode of the current transform block; and an encoding module configured to obtain encoded bits based on the predicted value of the attribute information of the current transform block and write the encoded bits into a bitstream.

[0025] In a fourteenth aspect, embodiments of this application provide an encoding apparatus applied to a point cloud encoder. The apparatus includes: a fourth determining module configured to determine a prediction mode of the current transform block of the current transform layer based on a predefined fourth-layer prediction mode of the lowest layer when the current transform layer is the lowest layer of the current point cloud; the fourth-layer prediction mode includes one or more prediction modes; a fifth determining module configured to determine a predicted value of the attribute information of the current transform block based on the prediction mode of the current transform block; and an encoding module configured to obtain encoded bits based on the predicted value of the attribute information of the current transform block and write the encoded bits into a bitstream.

[0026] In a fifteenth aspect, embodiments of this application provide a point cloud encoder, including a second memory and a second processor; wherein the second memory is used to store a computer program that can run on the second processor; and the second processor is used to execute the encoding method of embodiments of this application when running the computer program.

[0027] In a sixteenth aspect, embodiments of this application provide an electronic device, including: a processor adapted to execute a computer program; a computer-readable storage medium storing a computer program, wherein when the computer program is executed by the processor, it implements the decoding method of embodiments of this application, or when the computer program is executed by the processor, it implements the encoding method of embodiments of this application.

[0028] In a seventeenth aspect, embodiments of this application provide a computer-readable storage medium storing a computer program that, when executed, implements a decoding method or an encoding method of embodiments of this application.

[0029] In an eighteenth aspect, embodiments of this application provide a computer program product, including computer program instructions that cause a computer to execute the decoding method of embodiments of this application or the encoding method of embodiments of this application.

[0030] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0031] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the specification, serve to explain the technical solutions of this application. Obviously, the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0032] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0033] Figure 1 is a schematic diagram of the encoding process based on Region Adaptive Hierarchical Transform (RAHT).

[0034] Figure 2 is a schematic diagram of the decoding process based on RAHT transform;

[0035] Figure 3 is a schematic diagram of a RAHT transformation;

[0036] Figure 4 is a schematic diagram of the RAHT upsampling prediction positive transform;

[0037] Figure 5 is a schematic diagram of the RAHT inverse transform;

[0038] Figure 6 is a schematic diagram of inter-frame prediction based on RAHT transform;

[0039] Figure 7 is a schematic diagram of the implementation process of the decoding method provided in the embodiment of this application;

[0040] Figure 8 is a schematic diagram of the implementation process of the decoding method provided in the embodiment of this application;

[0041] Figure 9 is a schematic diagram of the implementation flow of the decoding method provided in the embodiment of this application;

[0042] Figure 10 is a schematic diagram of the implementation process of the encoding method provided in the embodiment of this application;

[0043] Figure 11 is a schematic diagram of the implementation process of the encoding method provided in the embodiment of this application (II).

[0044] Figure 12 is a schematic diagram of the implementation flow of the encoding method provided in the embodiment of this application;

[0045] Figure 13 is a schematic diagram of the encoding end operation flow provided in the embodiment of this application;

[0046] Figure 14 is a schematic diagram of the code stream structure of related technologies;

[0047] Figure 15 is a schematic diagram of the code stream structure according to an embodiment of this application;

[0048] Figure 16 is a schematic diagram of the decoding end operation flow provided in the embodiment of this application;

[0049] Figure 17 is a schematic diagram of the decoding device provided in an embodiment of this application;

[0050] Figure 18 is a second structural schematic diagram of the decoding device provided in an embodiment of this application;

[0051] Figure 19 is a schematic diagram of the structure of the decoding device provided in an embodiment of this application;

[0052] Figure 20 is a schematic diagram of the structure of the encoding device provided in an embodiment of this application;

[0053] Figure 21 is a second structural schematic diagram of the encoding device provided in an embodiment of this application;

[0054] Figure 22 is a schematic diagram of the structure of the encoding device provided in the embodiment of this application;

[0055] Figure 23 is a schematic diagram of the point cloud decoder provided in an embodiment of this application;

[0056] Figure 24 is a schematic diagram of the structure of the point cloud encoder provided in the embodiment of this application. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the specific technical solutions of this application will be further described in detail below with reference to the accompanying drawings of the embodiments of this application. The following embodiments are used to illustrate this application, but do not limit the scope of this application.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit this application.

[0059] In the following description, references are made to “some embodiments,” which describe a subset of all possible embodiments. However, it is 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.

[0060] In RAHT encoding / decoding mode, terms such as "current block to be encoded," "current block," "current node to be encoded," and "current node" appearing in this article can all be understood as "current transform block." Similarly, "predicted transform coefficients of the current transform block" can be understood as "predicted attribute transform values ​​of the current transform block," "predicted attribute transform coefficients of the current transform block," or "predicted attribute information of the current transform block," and so on.

[0061] The “inter-frame prediction mode” mentioned in this paper can also be called “inter-frame prediction”, the “intra-frame prediction mode” mentioned in this paper can also be called “intra-frame prediction”, the “no prediction mode” mentioned in this paper can also be called “no prediction”, the “average prediction mode” mentioned in this paper can also be called “average prediction”, and so on.

[0062] The encoding and decoding framework for geometry-based point cloud compression (G-PCC) includes three attribute encoding and decoding methods: Predicting Transform (PT), Lifting Transform (LT), and Region Adaptive Hierarchical Transform (RAHT). The first two methods predictively encode the point cloud based on the order in which Level of Detail (LOD) is generated, while RAHT adaptively transforms the attribute information based on the hierarchical structure of a multi-way tree (such as an octree).

[0063] In one implementation, the key to the RAHT transform lies in the following: for a hierarchical tree structure, a recursive transformation is performed from the root node to the child nodes from top to bottom. The low-frequency coefficients (DC) obtained from the transformation are passed to the next layer, while the high-frequency coefficients (AC) are quantized and encoded. The main encoding process is as follows: based on the octree structure of the point cloud, it is determined whether upsampling prediction or inter-frame prediction is used; secondly, a recursive transformation is performed from the root node to the child nodes from top to bottom to obtain the AC coefficients layer by layer. If prediction is involved, the difference between the predicted value and the original value of the AC coefficient is used to obtain the residual value of the AC coefficient (i.e., the prediction residual); finally, the residual value of the AC coefficient is quantized and encoded to generate the attribute information bitstream.

[0064] Schematably, as shown in Figure 1, for intra-frame prediction, the original point cloud is upsampled and predicted 101 to obtain a predicted point cloud. The predicted point cloud is then subjected to a RAHT transform 102 to obtain the predicted values ​​of the DC coefficients and all AC coefficients of the root node. Conversely, the original point cloud is also subjected to a RAHT transform 102 to obtain the DC coefficients and all AC coefficients of the root node. For inter-frame prediction, adjacent frames are used as the predicted point clouds of the original point cloud, and a RAHT transform 102 is applied to them to obtain the predicted values ​​of the DC coefficients and all AC coefficients of the root node. Based on the DC coefficients and all AC coefficients of the root node obtained from intra-frame and / or inter-frame prediction, and the DC coefficients and all AC coefficients of the root node obtained from the original point cloud, the prediction residual is determined. The prediction residual is then quantized 103, and the quantized prediction residual is entropy encoded 104 to generate an attribute bitstream. In one possible implementation, the DC coefficients and AC coefficients of the root node obtained from the original point cloud can be quantized and encoded to generate an attribute bitstream.

[0065] Schematic, as shown in Figure 2, at the decoding end, RAHT decoding still proceeds from the root node to the child nodes from top to bottom. The decoder reads the attribute bitstream and performs entropy decoding 201, followed by inverse quantization 202 to obtain the AC prediction residual (i.e., the residual value of the AC coefficients). If there is intra-frame prediction or inter-frame prediction, the AC prediction residual is added to the AC prediction value (i.e., the predicted value of the AC coefficients) to obtain the original AC coefficients. Then, it is combined with the DC coefficients and subjected to RAHT inverse transform 203 to obtain the reconstructed attribute value of this layer. The reconstructed attribute value of this layer can then be used to calculate the DC coefficients of the next layer, until all layers have been traversed to obtain the reconstructed attribute value. The following section will describe the RAHT predictive coding process in detail according to the above steps.

[0066] (1) RAHT Transformation:

[0067] In the RAHT transformation method used in G-PCC, the transformation is first performed recursively from the parent node to the child node along each dimension based on the partitioned octree structure. The transformation process is obtained by the following formula:

[0068] Where w i,j Let g be the weight of the j-th node to be transformed in the i-th layer. i,j h is the attribute value of the leaf node. i,j Let g′ be the AC coefficient. i,j The DC coefficients are used as the transformation coefficients. After each transformation, the DC coefficients are directly passed to the next layer, while the AC coefficients are quantized and entropy encoded. If there is only one node in the layer, the attribute value of that node is directly passed to the next layer as the DC coefficient. The transformation process is shown in Figure 3.

[0069] (2) Intra-frame prediction based on upsampling prediction:

[0070] To further remove redundancy and improve point compression efficiency, an upsampling prediction method is introduced. The core of upsampling prediction is intra-frame prediction, which uses the attribute information of pre-encoded points to predict the attribute information of the current point, thereby obtaining the predicted values ​​of the AC coefficients. Subsequently, redundancy is removed by using the residual between the predicted values ​​of the encoded AC coefficients and the true values ​​of the AC coefficients.

[0071] The RAHT transform uses a top-down tree structure, with the transformation performed within a 2×2×2 block. The reconstructed attribute values ​​of the parent node and its coplanar and collinear neighbors are used to predict the attribute values ​​of the child nodes. The true and predicted attribute values ​​of these child nodes within the block are then subjected to RAHT transform to obtain the corresponding DC and AC coefficients. The AC coefficients obtained based on the true and predicted attribute values ​​are then subtracted to obtain the residual AC coefficients. This residual is then quantized and entropy-encoded, as shown in Figure 4. During the inverse transform, the DC coefficients inherit the reconstructed attribute values ​​from the parent node. The residual AC coefficients obtained from the decoding end are accumulated with the AC coefficients obtained from the upsampled predicted attribute values, and then combined with the inherited DC coefficients for RAHT inverse transform to obtain the reconstructed attribute values, as shown in Figure 5.

[0072] (3) Inter-frame prediction mode:

[0073] Inter-frame prediction utilizes information from already encoded frames to predictively encode the current frame, reducing redundancy. The reference frame is partitioned into an octree structure. After undergoing RAHT transform, the AC coefficients of each reference node are memorized for inter-frame prediction in the next frame. In the target node encoding, the transform coefficients of the reference frame and the predicted transform coefficients of the current frame are used to determine the residual values ​​of the transform coefficients, which are then encoded. The decoder follows the same process. The inter-frame prediction process is shown in Figure 5. The reconstructed attribute values ​​of the target node in the reference frame, obtained through RAHT transform, are memorized as parameters 0-7 (i.e., one DC coefficient and seven AC coefficients), and used as the predicted coefficient values ​​for the target node in the current frame. The difference between the predicted coefficient values ​​and the actual coefficient values ​​of the target node in the current frame is used to obtain the coefficient residual. Entropy encoding is performed on the coefficient residual to generate the bitstream.

[0074] In one possible implementation, inter-frame prediction is applied only if the point clouds of the current frame and the reference frame have the same octree partitioning structure and are at the same node position. Inter-frame prediction is applied if AC coefficients exist in the reference frame's buffer. If the corresponding AC coefficients do not exist in the reference frame's buffer, inter-frame prediction is not applied.

[0075] (4) Average forecasting model:

[0076] In G-PCC, it is recommended to perform RAHT average prediction for certain specific layers.

[0077] For the first N levels of the octree decomposition, inter-frame prediction is enabled. If the inter-frame predicted value is not zero, it replaces the intra-frame predicted value. For the last M levels of the octree decomposition, average prediction is enabled. When both the inter-frame and intra-frame predicted values ​​are not zero, the average predicted value replaces the intra-frame predicted value. Otherwise, when the inter-frame predicted value is not zero, it replaces the intra-frame predicted value. In all other cases, the intra-frame predicted value is used as the predicted value.

[0078] When average prediction is enabled in GPCC, the prediction value is calculated as a weighted average of the inter-frame prediction value Attrinter_predict and the intra-frame prediction value Attrrintra_predict, using the following formula: Attraverage_predict

[0079] The weights w of the inter-frame prediction values inter The weights w of the intra-frame prediction values intra The values ​​are determined based on the number of voteInter and voteIntra, as shown below.

[0080] Where voteInter and voteIntra are the number of inter-frame prediction modes and intra-frame prediction modes of the parent node, parent neighbor node, and sibling node, respectively, calculated as follows:

[0081] - If a parent neighbor node applies intra-frame prediction / inter-frame prediction / no prediction, then voteInter is increased by 2 / voteIntra is increased by 2 / voteInter is increased by 1 and voteIntra is increased by 1 respectively.

[0082] - If a sibling node applies intra-frame prediction / inter-frame prediction / no prediction, then voteInter is increased by 6 / voteIntra is increased by 6 / voteInter is increased by 3 and voteIntra is increased by 3 respectively.

[0083] - If the parent node applies intra-frame prediction / inter-frame prediction / no prediction, then voteInter is increased by 12 / voteIntra is increased by 12 / voteInter is increased by 6 and voteIntra is increased by 6 respectively.

[0084] (5) Layer-optimal prediction mode selection based on rate-distortion optimization (RDO):

[0085] The latest version of G-PCC introduces a layer-optimal prediction mode selection scheme based on RDO selection. This scheme strictly specifies the selection of the optimal prediction mode (inter-frame prediction, intra-frame prediction, average prediction, no prediction) for each layer, as shown in Table 1. The detailed explanation of this table is as follows:

[0086] First, the RAHT transform layer is divided from the root node to the leaf node from top to bottom. The upper layer is defined as the first 3 layers from the root node downwards; the lower layer is defined as the last 2 layers from the leaf node upwards. These two layers are further divided: the leaf node layer is the lower layer with average prediction disabled, and the second to last layer is the lower layer with average prediction enabled; the remaining layers are the middle layers. The middle layers are also further divided, with the bottom layer of the middle layer (the third to last layer from the leaf node layer) being the layer with average prediction enabled, and the rest being the layers with average prediction disabled.

[0087] In G-PCC, the parameters upper_mode_level, mode_level, lower_mode_level_for_average_prediction, and upper_mode_level_for_average_prediction are first defined in the attribute APS. These variables indicate the number of upper layers, the number of lower layers, the number of lower layers with average prediction enabled, and the number of middle layers with average prediction enabled, respectively. The layer procedure APS is shown below:

[0088] aps.rahtPredParams.upper_mode_level,4

[0089] aps.rahtPredParams.mode_level,2

[0090] aps.rahtPredParams.lower_mode_level_for_average_prediction,1

[0091] aps.rahtPredParams.upper_mode_level_for_average_prediction,1

[0092] Subsequently, in the codec, an inference process is executed at each layer to determine which layer is currently in operation; taking the inference at the upper layer as an example, the steps are as follows:

[0093] First, create a boolean variable `upperInferMode`, with a value of 1 indicating it's in the upper level; otherwise, it's not. Then, the program infers: the distance from the root node is less than the maximum preset number of upper levels, and the total number of levels below the current level is greater than the total number of levels above it. If these conditions are met, the inference value is 1.

[0094] bool upperInferMode=

[0095] distanceToRoot <rahtPredParams.upper_mode_level

[0096] &&distanceToRoot <layerDepth-rahtPredParams.mode_level+1;

[0097] Subsequently, for each layer, there are at least two layer prediction methods to choose from. There are three types of layer prediction methods in total: OrgCodingMethod, Inter-layerCodingMethod, and Intra-layerCodingMethod. The selection of these three layer prediction methods depends on the layer coefficient RDO.

[0098] When the RDO selects a layer prediction mode, it can find the optimal prediction mode execution status for each layer according to Table 1. For example, "Inter>Intra>Null" means that if the inter-frame prediction value is not 0, then inter-frame prediction is used; if inter-frame prediction does not exist or its value is 0, then it checks whether the intra-frame prediction value is 0. If the intra-frame prediction value is not 0, then intra-frame prediction is used; otherwise, no prediction is used. Another example is "Inter,Intra,Null RDO selection," which means that for each RAHT transform block in this layer, the intra-layer RDO is selected from the three prediction modes of intra-frame prediction, inter-frame prediction, and no prediction, and the optimal prediction mode is chosen.

[0099] Thus, each RAHT transform coefficient has a complete prediction mode selection scheme. At the encoding end, the optimal prediction mode is entropy-encoded; layers with two prediction modes (i.e., layer prediction modes) are encoded using 0,1, and layers with three prediction modes (i.e., layer prediction modes) are encoded using 0,01,11. At the decoding end, the optimal prediction mode flag is decoded, and based on this, the predicted values ​​of the AC coefficients can be obtained.

[0100] Table 1. Details of the optimal prediction model for the RAHT layer.

[0101] In G-PCC, the encoding and decoding operations are as follows: On the encoding side, `upperInferMode` is used to define the upper layer, and `realInferInLowerLevel` is used to define the lower layer that disables average prediction. Therefore, for two layers, one bit (0,1) is used for encoding; other layers use truncated unary codes (0,01,11).

[0102] On the decoding side, upperInferMode is used to define the upper layer, and realInferInLowerLevel is used to define the lower layer that disables average prediction. In these two layers, one byte is decoded, and the remaining layers are decoded according to the truncated unary code rule.

[0103] (6) Coding coefficient residuals and residual RDOQ:

[0104] The predicted attribute values ​​of each point in the current 2×2×2 block are obtained through the above intra-frame prediction or inter-frame prediction. The actual and predicted attribute values ​​of these intra-block child nodes are then subjected to RAHT transformation to obtain the corresponding DC and AC coefficients. The predicted value of the i-th AC coefficient is expressed as follows: (k is 8). Let (AC) i ) i∈1…k-1 For the i-th true AC coefficient, the encoded AC coefficient residual (r) i ) i∈0…k-1 Recorded as:

[0105] Then, rate-distortion optimization judgment is performed on the residual of AC coefficient. If the rate-distortion cost RDcost of setting the coefficient to 0 is less than the rate-distortion cost RDcost of the original encoding, then the coefficient is set to 0.

[0106] Further quantification of the prediction residuals after RDO judgment:

[0107] In the formula Q i This represents the attribute residual after quantization at the current point i. Qs is the quantization step size, which can be calculated from the quantization parameter QP specified by CTC.

[0108] (7) Reconstruct attribute values ​​at the encoding end:

[0109] The purpose of encoding-end reconstruction is for the prediction of subsequent points. Before reconstructing attribute values, the encoded AC residuals need to be dequantized, denoted as... The residual after dequantization:

[0110] With predicted AC coefficient The sums are used to obtain the i-th reconstruction AC coefficient within the current block.

[0111] Finally, the reconstructed AC coefficients were analyzed. The reconstructed attribute values ​​can be obtained by performing an inverse RAHT transformation together with the DC coefficients inherited from the parent node at the previous level.

[0112] Region Adaptive Transform (RAHT) can perform layer-by-layer computation and quantization encoding from the root node to the child nodes. In the current AC coefficient layer RDO prediction mode, rate-distortion optimization selects the optimal layer prediction mode from three layer prediction modes: OrgCodingMethod, Inter-layerCodingMethod, and Intra-layerCodingMethod. Then, according to Table 1, the AC prediction mode (inter-frame prediction / intra-frame prediction / average prediction / no prediction) for the intra-layer transform block is determined. However, for multi-frame dynamic point clouds, in the upper layers near the root node in RAHT transform, the attribute values ​​within larger transform blocks change almost zero between adjacent frames. Therefore, the inter-frame prediction values ​​of AC coefficients in the upper layers near the root node are relatively accurate. Thus, the priority intra-frame prediction scheme in the Intra-layerCodingMethod layer prediction mode is unreasonable. Statistical evidence shows that in the upper layers near the root node of multi-frame dynamic point clouds, the layer RDO does not select the Intra-layerCodingMethod layer prediction mode. Therefore, the computation and encoding of Intra-layer CodingMethod within these layers will inevitably cause redundancy in time and bit rate.

[0113] Based on the above analysis, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0114] As mentioned above, the current point cloud transformation layer is divided into upper, middle, and lower layers. Depending on the layer to which the current transformation layer belongs (e.g., upper, middle, or lower), this application provides corresponding decoding and encoding methods. For example, Embodiment 1 and its further or additional embodiments described below are decoding method embodiments for the current transformation layer belonging to the upper layer; Embodiment 2 and its further or additional embodiments described below are decoding method embodiments for the current transformation layer belonging to the upper-middle layer; and Embodiment 3 and its further or additional embodiments described below are decoding method embodiments for the current transformation layer belonging to the lowest layer. The point cloud decoder can support decoding methods combining any one or more embodiments from Embodiment 1 and its further or additional embodiments, Embodiment 2 and its further or additional embodiments, and Embodiment 3 and its further or additional embodiments.

[0115] Example 1:

[0116] This application provides a decoding method that can be applied to a point cloud decoder. Figure 7 is a schematic diagram of the implementation flow of the decoding method provided in this application. As shown in Figure 7, the method includes the following steps 701 to 703:

[0117] Step 701: If the current transformation layer is the upper layer of the current point cloud, determine the prediction mode of the current transformation block of the current transformation layer according to the predefined first-layer prediction mode of the upper layer; the first-layer prediction mode includes one or more prediction modes.

[0118] Step 702: Determine the predicted values ​​of the attribute information of the current transform block based on the prediction mode of the current transform block;

[0119] Step 703: Determine the attribute information of the current transform block based on the predicted values ​​of the attribute information of the current transform block.

[0120] It is understood that in the embodiments of this application, for the current transform layer that belongs to the upper layer of the current point cloud, its layer prediction mode is the predefined first layer prediction mode, rather than being parsed from the bitstream; thus, it saves bitstream overhead and is also beneficial to improving encoding and decoding efficiency.

[0121] The following describes and illustrates further or additional embodiments of Embodiment 1.

[0122] In step 701, if the current transformation layer is the upper layer of the current point cloud, the prediction mode of the current transformation block of the current transformation layer is determined according to the predefined first-layer prediction mode of the upper layer; the first-layer prediction mode includes one or more prediction modes.

[0123] In this embodiment, the current point cloud can be a frame-level or slice-level point cloud. Therefore, the current point cloud can be understood as the current frame, or it can also be understood as the current slice.

[0124] It should be noted that in the embodiments of this application, the "first" in "first-layer prediction mode" does not specifically refer to the first-layer prediction mode, and the "second" in "second-layer prediction mode" mentioned below does not refer to the second-layer prediction mode. Similarly, the "third" in "third-layer prediction mode" and the "fourth" in "fourth-layer prediction mode," and similar descriptions, do not specifically refer to the third / fourth-layer prediction modes. The terms "first," "second," "third," or "fourth," etc., here have no substantial meaning; their purpose is to facilitate a clear description of the technical solutions provided in the embodiments of this application. One or more of these layer prediction modes may be the same or different, and this application does not impose any limitations on this.

[0125] In this embodiment, the first-layer prediction mode is not limited; it is a layer prediction mode that includes one or more prediction modes. In summary, for the current transform layer belonging to the upper layer, the prediction mode of its current transform block is determined based on the predefined first-layer prediction mode.

[0126] In some embodiments, the first-layer prediction mode includes an inter-frame prediction mode, in which the inter-frame prediction mode takes precedence.

[0127] It is understandable that the so-called inter-frame prediction mode priority means that when determining the prediction mode of the current transform block in the current transform layer, it is prioritized to determine whether an inter-frame prediction mode can be used. For example, if there is a transform block in the reference frame that is at the same level and position as the current transform block, then the prediction mode of the current transform block is the inter-frame prediction mode.

[0128] As analyzed above, for multi-frame dynamic point clouds, in the RAHT transform, the attribute values ​​within larger transform blocks near the root node change almost zero between adjacent frames. Therefore, in the upper layers near the root node, the inter-frame prediction values ​​of the AC coefficients are relatively accurate. Consequently, the intra-frame prediction priority scheme in the Intra-layer CodingMethod prediction mode is unreasonable. Therefore, in this embodiment, for transform layers belonging to the upper layers, the possible layer prediction modes do not include the Intra-layer CodingMethod, i.e., layer prediction modes prioritizing intra-frame prediction are not included. Thus, for the decoder, determining the prediction mode of the current transform block belonging to the upper transform layer based on the predefined first layer prediction mode can save bitstream overhead without sacrificing the prediction accuracy of the current transform block. Furthermore, since it is not necessary to determine the layer prediction mode of the upper transform layer through decoding the bitstream, it is beneficial to improve the decoding efficiency of the current point cloud.

[0129] As mentioned above, the first-layer prediction mode includes an inter-frame prediction mode, and the inter-frame prediction mode takes precedence. Furthermore, in some embodiments, the first-layer prediction mode further includes one or more of the following prediction modes:

[0130] Intra-frame prediction mode;

[0131] Unpredictable patterns;

[0132] Average forecast pattern.

[0133] For example, in some embodiments, the first-layer prediction mode includes an inter-frame prediction mode and an intra-frame prediction mode, wherein the inter-frame prediction mode has a higher priority than the intra-frame prediction mode.

[0134] For example, in some embodiments, the first-layer prediction mode includes an inter-frame prediction mode, an intra-frame prediction mode, and a no-prediction mode.

[0135] For example, in some embodiments, the first-layer prediction mode includes an inter-frame prediction mode, an intra-frame prediction mode, and a no-prediction mode; and in the first-layer prediction mode, the priority of the prediction modes from high to low is: inter-frame prediction mode, intra-frame prediction mode, and no-prediction mode. This priority relationship can also be expressed as "Inter>Intra>Null". In one possible implementation, the first-layer prediction mode is OrgCodingMethod, as shown in Table 2 below. If it is known that the current transform layer is an upper layer and the layer prediction mode is OrgCodingMethod, the layer prediction mode of the current transform layer can be determined to be "Inter>Intra>Null".

[0136] Table 2. Details of the optimal prediction model for the RAHT layer.

[0137] In step 702, the predicted values ​​of the attribute information of the current transform block are determined according to the prediction mode of the current transform block.

[0138] In some embodiments, the attribute information of the current transform block can be understood as the attribute information of the attribute values ​​of the current transform block in the transform domain. For example, the attribute information of the current transform block includes the transform coefficients of the current transform block, which may be AC ​​coefficients or DC coefficients.

[0139] In one possible implementation, the attribute values ​​of the child nodes / sub-transform blocks of the current transform block can be predicted based on the prediction mode of the current transform block to obtain the predicted attribute values ​​of the child nodes / sub-transform blocks of the current transform block; then, the predicted attribute values ​​of the child nodes / sub-transform blocks of the current transform block are subjected to RAHT transformation to obtain the predicted values ​​of the AC coefficients and DC coefficients of the current transform block, which are the predicted values ​​of the transform coefficients of the current transform block.

[0140] In another possible implementation, the predicted values ​​of the transform coefficients of the current transform block can be determined directly in the transform domain. In the transform domain, the transform coefficients (such as AC coefficients) of the current transform block are predicted according to the prediction mode of the current transform block to obtain the predicted values ​​of the transform coefficients of the current transform block.

[0141] In step 703, the attribute information of the current transform block is determined based on the predicted value of the attribute information of the current transform block.

[0142] It should be noted that, in the embodiments of this application, the attribute information of the current transform block obtained in step 703 can be understood as the reconstructed value of the attribute information of the current transform block. For embodiments where the attribute information of the current transform block can be the attribute information of the transform domain, the attribute information of the current transform block finally determined in step 703 can be understood as the transform coefficients (such as AC coefficients) of the current transform block, which are reconstructed transform coefficients, that is, the reconstructed values ​​of the transform coefficients.

[0143] In some embodiments, the decoding method further includes: decoding the bitstream to determine the residual value of the attribute information of the current transform block of the current transform layer; for step 703, determining the attribute information of the current transform block based on the predicted value of the attribute information of the current transform block includes: determining the attribute information of the current transform block based on the residual value and the predicted value of the attribute information of the current transform block.

[0144] For lossy compression point cloud encoding and decoding, at the decoding end, the decoder decodes the bitstream to obtain the residual value of the attribute information of the current transform block. Then, the residual value is dequantized, and the predicted value of the attribute information of the current transform block is accumulated with the dequantized residual value. The accumulated result is the attribute information of the current transform block obtained in step 703, which is the reconstructed value.

[0145] For example, in some embodiments, the residual value of the attribute information of the current transform block includes the residual value of the AC coefficient of the current transform block, and the predicted value of the attribute information of the current transform block includes the predicted value of the AC coefficient of the current transform block.

[0146] In one possible implementation, the attribute information of the current transform block is determined based on the residual and predicted values ​​of its attribute information. This includes: dequantizing the residual values ​​of the AC coefficients of the current transform block; and determining the AC coefficients of the current transform block based on the residual values ​​of the dequantized AC coefficients and the predicted values ​​of the AC coefficients of the current transform block. For example, the AC coefficients of the current transform block are equal to the sum of the residual values ​​of the dequantized AC coefficients and the predicted values ​​of the AC coefficients of the current transform block.

[0147] For lossless compression point cloud encoding and decoding, at the decoding end, the decoder decodes the bitstream to obtain the residual value of the attribute information of the current transform block. The final attribute information of the current transform block can be the sum of the residual value and the predicted value of the attribute information of the current transform block.

[0148] In one possible implementation, the attribute information of the current transform block is determined based on the residual value and the predicted value of the attribute information of the current transform block, including: the AC coefficients of the current transform block are equal to the sum of the residual value of the AC coefficients and the predicted value of the AC coefficients of the current transform block.

[0149] In some embodiments, the decoding method further includes: when the current transform layer is a middle or upper layer of the current point cloud, decoding the bitstream to determine a fifth syntax element; determining the layer prediction mode of the current transform layer based on the fifth syntax element; wherein, when the current transform layer is a middle or upper layer, the layer prediction mode indicated by the fifth syntax element is any one of the fifth, sixth, and seventh layer prediction modes; determining the prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer. Subsequently, the attribute information of the current transform block of the current transform layer is determined according to steps 702 and 703.

[0150] For example, in some embodiments, the fifth-layer prediction mode can be the prediction mode of the OrgCodingMethod layer. For the current transform layer belonging to the upper-middle layer, as shown in Table 1 mentioned above, the upper-middle layer can belong to the middle layer's disabled average prediction layer. Therefore, the fifth-layer prediction mode of this layer can include inter-frame prediction mode, intra-frame prediction mode, and no prediction mode. When the fifth syntax element indicates the fifth-layer prediction mode, the decoder also needs to decode the bitstream to determine the eighth syntax element. Based on the value of the eighth syntax element, the prediction mode of the current transform block of the current transform layer is determined. The eighth syntax element is used to indicate the prediction mode of the current transform block in the fifth-layer prediction mode.

[0151] In some embodiments, the sixth-layer prediction mode includes an inter-frame prediction mode, and the inter-frame prediction mode has priority. For example, in some embodiments, the sixth-layer prediction mode can be the prediction mode of the Inter-layer CodingMethod layer. For the current transform layer belonging to the upper-middle layer, as shown in Table 1 above, the upper-middle layer can be the disabled average prediction layer of the middle layer. The sixth-layer prediction mode of this layer can include an inter-frame prediction mode, an intra-frame prediction mode, and a no-prediction mode. In the sixth-layer prediction mode, the priority of the prediction modes from high to low can be: inter-frame prediction mode, intra-frame prediction mode, and no-prediction mode.

[0152] In some embodiments, the seventh-layer prediction mode includes an intra-layer prediction mode, in which the intra-layer prediction mode takes precedence. For example, in some embodiments, the sixth-layer prediction mode may be an Intra-layer CodingMethod. Therefore, for the current transform layer belonging to the upper-middle layer, as shown in Table 1 above, the upper-middle layer may be a disabled average prediction layer of the middle layer. The seventh-layer prediction mode of this layer may include an intra-layer prediction mode and a no-prediction mode, wherein the intra-layer prediction mode has higher priority than the no-prediction mode.

[0153] In some embodiments, the decoding method further includes: when the current transform layer is the lowest layer of the current point cloud, decoding the bitstream to determine a sixth syntax element; determining the layer prediction mode of the current transform layer based on the sixth syntax element; wherein, when the current transform layer is the lowest layer, the layer prediction mode indicated by the sixth syntax element is either the eighth layer prediction mode or the ninth layer prediction mode; and determining the prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer. Subsequently, the attribute information of the current transform block of the current transform layer is determined according to steps 702 and 703.

[0154] In some embodiments, the eighth-layer prediction mode includes an intra-prediction mode, and the intra-prediction mode takes precedence. For example, in some embodiments, as shown in Table 1 above, the lowest layer may be a lower-level disabled average prediction layer, and the eighth-layer prediction mode may be an OrgCodingMethod. Therefore, for the current transform layer belonging to the lowest layer, the eighth-layer prediction mode includes an intra-prediction mode and a no-prediction mode, wherein the intra-prediction mode has a higher priority than the no-prediction mode.

[0155] In some embodiments, the ninth-layer prediction mode includes an inter-frame prediction mode, and the inter-frame prediction mode takes precedence. For example, in some embodiments, as shown in Table 1 above, the bottom layer may be a lower-layer disabled average prediction layer, and the ninth-layer prediction mode may be an Inter-layer CodingMethod. Therefore, for the current transform layer belonging to the bottom layer, the ninth-layer prediction mode includes an inter-frame prediction mode, an intra-frame prediction mode, and a no-prediction mode. In the ninth-layer prediction mode, the order of priority of the prediction modes from high to low may be: inter-frame prediction mode, intra-frame prediction mode, and no-prediction mode.

[0156] Example 2:

[0157] This application provides a decoding method that can be applied to a point cloud decoder. Figure 8 is a schematic diagram of the implementation flow of the decoding method provided in this application. As shown in Figure 8, the method includes the following steps 801 to 805:

[0158] Step 801: If the current transform layer is a middle or upper layer of the current point cloud, decode the bitstream and determine the first syntax element;

[0159] Step 802: Determine the layer prediction mode of the current transform layer based on the first syntax element;

[0160] Step 803: Determine the prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer;

[0161] Step 804: Determine the predicted values ​​of the attribute information of the current transform block based on the prediction mode of the current transform block.

[0162] Step 805: Determine the attribute information of the current transform block based on the predicted value of the attribute information of the current transform block.

[0163] The following describes and illustrates further or additional embodiments of Embodiment 2.

[0164] In step 801, if the current transform layer is a middle or upper layer of the current point cloud, the bitstream is decoded to determine the first syntax element.

[0165] In some embodiments, the upper-middle layer of the current point cloud refers to the transformation layer in the middle layer of the current point cloud and close to the root node. In the embodiments of this application, the method for determining whether the current transformation layer is the upper-middle layer of the current point cloud is not limited.

[0166] In some embodiments, the decoding method further includes: decoding the bitstream and determining a third syntax element; wherein the third syntax element is used to indicate the position of the current transform layer in the middle layer; wherein the value of the third syntax element is equal to a first value, indicating that the current transform layer is in the upper-middle layer of the middle layer.

[0167] In other embodiments, it can also be determined by calculation whether the current transformation layer belongs to the upper-middle layer. In one possible implementation, a maximum number of layers parameter is added to the APS, defined as 3, i.e.:

[0168] aps.rahtPredParams.upper_in_middle_mode_level,3

[0169] Subsequently, an inference procedure was added to the codec, as follows:

[0170] First, create a boolean variable `upperInMiddleLevel`, with a value of 1 indicating that it is in the upper middle level, and otherwise not in the upper middle level.

[0171] The program then infers that the distance from the current transformation layer to the root node is greater than the number of upper layers and less than (the number of upper layers + half the number of middle layers); additionally, the number of upper-middle layers is less than the corresponding maximum preset value. If the above conditions are met, then upperInMiddleLevel is inferred to be 1, meaning the current transformation layer is an upper-middle layer. For example, the following computer program can be used to determine whether the current transformation layer is an upper-middle layer:

[0172] In the embodiments of this application, there is no limitation on the layer prediction mode of the upper and middle layers indicated by the first syntax element, which can indicate one or more layer prediction modes.

[0173] In some embodiments, the upper-middle layer prediction mode indicated by the first syntax element is either the second layer prediction mode or the third layer prediction mode.

[0174] It is understandable that the first syntax element indicates either the second or third layer prediction mode. Therefore, the first syntax element can indicate the middle and upper layer prediction mode with only 1 bit, without the need to use two or more bits to indicate the middle and upper layer prediction mode; thus, it is beneficial to save bitstream overhead.

[0175] In this embodiment, the second-layer prediction mode is not limited; it is a layer prediction mode that includes one or more prediction modes. Similarly, the third-layer prediction mode is also not limited; it is a layer prediction mode that includes one or more prediction modes. In summary, for the current transform layer belonging to the middle or upper layers, its layer prediction mode is either the second-layer or the third-layer prediction mode.

[0176] In some embodiments, the second-layer prediction mode includes an inter-frame prediction mode, in which the inter-frame prediction mode takes precedence.

[0177] It is understandable that the so-called inter-frame prediction mode priority means that when determining the prediction mode of the current transform block in the current transform layer, it is prioritized to determine whether an inter-frame prediction mode can be used. For example, if there is a transform block in the reference frame that is at the same level and position as the current transform block, then the prediction mode of the current transform block is the inter-frame prediction mode.

[0178] As mentioned above, the second-layer prediction mode includes an inter-frame prediction mode, with the inter-frame prediction mode taking precedence. Furthermore, in some embodiments, the second-layer prediction mode also includes one or more of the following prediction modes:

[0179] Intra-frame prediction mode;

[0180] Unpredictable patterns;

[0181] Average forecast pattern.

[0182] For example, in some embodiments, the second-layer prediction mode includes an inter-frame prediction mode and an intra-frame prediction mode, wherein the inter-frame prediction mode has a higher priority than the intra-frame prediction mode.

[0183] For example, in some embodiments, the second-layer prediction modes include inter-frame prediction mode, intra-frame prediction mode, and no prediction mode.

[0184] For example, in some embodiments, the priority of prediction modes in the second layer prediction mode, from high to low, is: inter-frame prediction mode, intra-frame prediction mode, and no prediction mode. This priority relationship can also be expressed as "Inter>Intra>Null". In one possible implementation, the second layer prediction mode is Inter-layerCodingMethod, as shown in Table 3 below. If it is known that the current transform layer is a middle-upper layer in a middle layer, and the layer prediction mode is Inter-layerCodingMethod, then the layer prediction mode of the current transform layer can be determined to be "Inter>Intra>Null".

[0185] It should be noted that, in the embodiments of this application, the upper middle layer can also be understood as the upper middle layer, that is, one or more transformation layers in the middle layer that are close to the root node.

[0186] Table 3. Details of the optimal prediction model for the RAHT layer

[0187] In some embodiments, the third-layer prediction mode includes one or more prediction modes. Further, in some embodiments, the third-layer prediction mode includes one or more of the following prediction modes:

[0188] Inter-frame prediction mode;

[0189] Intra-frame prediction mode;

[0190] Unpredictable patterns;

[0191] Average forecast pattern.

[0192] For example, in some embodiments, the third-layer prediction mode includes inter-frame prediction mode, intra-frame prediction mode, and no prediction mode. For example, in some embodiments, the third-layer prediction mode may be OrgCodingMethod, so for the current transform layer belonging to the middle or upper layers, the third-layer prediction mode can be determined to include inter-frame prediction mode, intra-frame prediction mode, and no prediction mode.

[0193] In steps 802 and 803, the layer prediction mode of the current transform layer is determined based on the first syntax element; and the prediction mode of the current transform block of the current transform layer is determined based on the layer prediction mode of the current transform layer.

[0194] It is understandable that the layer prediction model is oriented towards the transformation layer and is a layer-level prediction model. Furthermore, based on the prediction model of this layer, the block-level prediction model can be determined.

[0195] In some embodiments, when the layer prediction mode of the upper-middle layer indicated by the first syntax element is the second-layer prediction mode, the prediction mode of the current transform block of the current transform layer can be determined according to the priority of one or more prediction modes in the second-layer prediction modes. For example, in the second-layer prediction modes, Inter>Intra>Null, that is, the inter-frame prediction mode has the highest priority, followed by the intra-frame prediction mode, and finally the no-prediction mode. If the value of the inter-frame prediction is not 0, then inter-frame prediction is used; if the inter-frame prediction does not exist or its value is 0, then it is determined whether the value of the intra-frame prediction is 0. If the value of the intra-frame prediction is not 0, then intra-frame prediction is used; otherwise, no prediction is used.

[0196] In other embodiments, when the prediction mode of the upper-middle layer indicated by the first syntax element is the third-layer prediction mode, the bitstream is decoded to determine the second syntax element; the second syntax element is used to indicate the prediction mode of the current transform block of the current transform layer; the prediction mode of the current transform block is determined according to the value of the second syntax element.

[0197] As mentioned earlier, the third-layer prediction mode includes one or more prediction modes. For example, the third-layer prediction mode includes inter-frame prediction mode, intra-frame prediction mode, and no prediction mode. If the value of the second syntax element is the second value, the prediction mode of the current transform block is inter-frame prediction mode; if the value of the second syntax element is the third value, the prediction mode of the current transform block is intra-frame prediction mode; and if the value of the second syntax element is the fourth value, the prediction mode of the current transform block is no prediction mode.

[0198] In step 804, the predicted values ​​of the attribute information of the current transform block are determined according to the prediction mode of the current transform block.

[0199] For an understanding of step 804 and further embodiments, please refer to the previous description of step 702 and further embodiments. To avoid repetition, they will not be repeated here.

[0200] In step 805, the attribute information of the current transform block is determined based on the predicted value of the attribute information of the current transform block.

[0201] In some embodiments, the decoding method further includes: decoding the bitstream to determine the residual value of the attribute information of the current transform block of the current transform layer;

[0202] In some embodiments, step 805 may include: determining the attribute information of the current transform block based on the residual value and the predicted value of the attribute information of the current transform block.

[0203] For lossy compression point cloud encoding and decoding, at the decoding end, the decoder decodes the bitstream to obtain the residual value of the attribute information of the current transform block, and then dequantizes the residual value. The final attribute information of the current transform block can be the sum of the predicted value of the attribute information of the current transform block and the dequantized residual value.

[0204] For example, in some embodiments, the residual value of the attribute information of the current transform block includes the residual value of the AC coefficient of the current transform block, and the predicted value of the attribute information of the current transform block includes the predicted value of the AC coefficient of the current transform block.

[0205] In one possible implementation, the attribute information of the current transform block is determined based on the residual and predicted values ​​of its attribute information. This includes: dequantizing the residual values ​​of the AC coefficients of the current transform block; and determining the AC coefficients of the current transform block based on the residual values ​​of the dequantized AC coefficients and the predicted values ​​of the AC coefficients of the current transform block. For example, the AC coefficients of the current transform block are equal to the sum of the residual values ​​of the dequantized AC coefficients and the predicted values ​​of the AC coefficients of the current transform block.

[0206] For lossless compression point cloud encoding and decoding, at the decoding end, the decoder decodes the bitstream to obtain the residual value of the attribute information of the current transform block. The final attribute information of the current transform block can be the sum of the residual value and the predicted value of the attribute information of the current transform block.

[0207] In one possible implementation, the attribute information of the current transform block is determined based on the residual value and the predicted value of the attribute information of the current transform block, including: the AC coefficients of the current transform block are equal to the sum of the residual value of the AC coefficients and the predicted value of the AC coefficients of the current transform block.

[0208] In some embodiments, the decoding method further includes: when the current transform layer is an upper layer of the current point cloud, decoding the bitstream to determine a seventh syntax element; and determining the layer prediction mode of the current transform layer based on the seventh syntax element; wherein, when the current transform layer is an upper layer, the layer prediction mode indicated by the seventh syntax element is either the tenth layer prediction mode or the eleventh layer prediction mode. Subsequently, the attribute information of the current transform block of the current transform layer is determined according to steps 803 to 805.

[0209] In some embodiments, the tenth-layer prediction mode includes an inter-frame prediction mode, and the inter-frame prediction mode has priority. For example, in some embodiments, as detailed in Table 1 above, the tenth-layer prediction mode can be the prediction mode of the OrgCodingMethod layer. For the current transform layer belonging to the upper layer, the tenth-layer prediction mode of that layer can include an inter-frame prediction mode, an intra-frame prediction mode, and a no-prediction mode. In the tenth-layer prediction mode, the priority of the prediction modes from high to low can be: inter-frame prediction mode, intra-frame prediction mode, and no-prediction mode (Inter>Intra>Null).

[0210] In some embodiments, the eleventh-layer prediction mode includes an intra-layer prediction mode, and the intra-layer prediction mode takes precedence. For example, in some embodiments, as detailed in Table 1 above, the eleventh-layer prediction mode can be an Intra-layer CodingMethod. Therefore, for the current transform layer belonging to the upper layer, the eleventh-layer prediction mode includes an intra-layer prediction mode and a no-prediction mode, wherein the intra-layer prediction mode has a higher priority than the no-prediction mode (Intra>Nul).

[0211] In some embodiments, the decoding method further includes: when the current transform layer is the lowest layer of the current point cloud, decoding the bitstream to determine a sixth syntax element; determining the layer prediction mode of the current transform layer based on the sixth syntax element; and subsequently determining the attribute information of the current transform block of the current transform layer according to steps 803 to 805. Wherein, when the current transform layer is the lowest layer of the current point cloud, the layer prediction mode indicated by the sixth syntax element is either the eighth layer prediction mode or the ninth layer prediction mode.

[0212] Example 3:

[0213] This application provides a decoding method that can be applied to a point cloud decoder. Figure 9 is a schematic diagram of the implementation flow of the decoding method provided in this application. As shown in Figure 9, the method includes the following steps 901 to 903:

[0214] Step 901: When the current transformation layer is the lowest layer of the current point cloud, determine the prediction mode of the current transformation block of the current transformation layer according to the predefined fourth layer prediction mode of the lowest layer; the fourth layer prediction mode includes one or more prediction modes.

[0215] Step 902: Determine the predicted values ​​of the attribute information of the current transform block based on the prediction mode of the current transform block;

[0216] Step 903: Determine the attribute information of the current transform block based on the predicted value of the attribute information of the current transform block.

[0217] It is understood that in the embodiments of this application, for the current transform layer, which is the lowest layer of the current point cloud, its layer prediction mode is the predefined fourth layer prediction mode, rather than being parsed from the bitstream; thus, it saves bitstream overhead and is also beneficial to improving encoding and decoding efficiency.

[0218] The following describes and illustrates further or additional embodiments of Embodiment 3.

[0219] In step 901, if the current transformation layer is the lowest layer of the current point cloud, the prediction mode of the current transformation block of the current transformation layer is determined according to the predefined fourth-layer prediction mode of the lowest layer; the fourth-layer prediction mode includes one or more prediction modes.

[0220] In some embodiments, the lowest layer of the current point cloud can be one or more transformation layers among the lower layers of the current point cloud. Exemplarily, in some embodiments, the lowest layer of the current point cloud refers to the transformation layer containing the leaf nodes of the current point cloud and / or the transformation layer closest to the leaf nodes. For example, the lowest layer of the current point cloud may be a layer with average prediction disabled.

[0221] In this embodiment, no restrictions are placed on the method for determining whether the current transform layer is the lowest layer of the current point cloud. The layer to which the current point cloud belongs can be determined by parsing from the bitstream or by calculation.

[0222] In this embodiment, there is no limitation on the fourth-layer prediction mode, which is a layer prediction mode that includes one or more prediction modes. In summary, for the current transform layer that is the lowest layer, the prediction mode of its current transform block is determined based on the predefined fourth-layer prediction mode.

[0223] In some embodiments, the fourth-layer prediction mode includes an intra-frame prediction mode, in which the intra-frame prediction mode takes precedence.

[0224] This is understandable. The so-called "intra-prediction mode priority" means that when determining the prediction mode of the current transform block in the current transform layer, it is prioritized whether an intra-prediction mode can be used. For example, in some embodiments, the fourth-layer prediction mode includes an intra-prediction mode and a no-prediction mode, with the intra-prediction mode having a higher priority than the no-prediction mode. That is, in the fourth-layer prediction mode, Intra > Null. Therefore, it is prioritized to determine whether the value of the intra-predicted value is not 0. If it is not 0, the intra-prediction mode is used; otherwise, the no-prediction mode is used. In one possible implementation, the fourth-layer prediction mode can be OrgCodingMethod. As shown in Table 4, if it is known that the current transform layer is the lowest layer of the next layer (such as the disabled average prediction layer in the next layer), and the layer prediction mode is OrgCodingMethod, then the layer prediction mode of the current transform layer can be determined to be "Intra > Null".

[0225] Table 4. Details of the optimal prediction model for the RAHT layer

[0226] It should be noted that analysis revealed that for RAHT transform layers of point clouds, transform blocks near leaf nodes are at the voxel level or close to the voxel level. Therefore, for leaf node layers (i.e., the transform layers containing leaf nodes) and / or transform layers near leaf nodes, the attribute values ​​of transform blocks at the same level differ significantly between adjacent frames. If inter-frame prediction is used to determine the predicted values ​​of transform block attribute information within leaf node layers or transform layers near leaf nodes, the prediction accuracy is low, resulting in a large bit overhead for the residual values ​​written to the final bitstream. Therefore, in this embodiment, for the lowest transform layer of the current point cloud, the possible layer prediction modes do not include layer prediction modes that prioritize inter-frame prediction. For the lowest transform layer of the current point cloud, its layer prediction mode is the intra-prediction mode priority layer prediction mode. Thus, for the decoder, the prediction mode of the current transform block of the current transform layer belonging to the lowest transform layer can be determined according to the predefined intra-prediction mode priority fourth layer prediction mode, thereby saving bitstream overhead without losing the prediction accuracy of the current transform block. In addition, since it is not necessary to determine the layer prediction mode of the lowest transform layer through decoding the bitstream, it is beneficial to improve the decoding efficiency of the current point cloud.

[0227] In step 902, the predicted values ​​of the attribute information of the current transform block are determined according to the prediction mode of the current transform block.

[0228] For an understanding of step 902 and further embodiments, please refer to the previous description of step 702 and further embodiments. To avoid repetition, they will not be repeated here.

[0229] In step 903, the attribute information of the current transform block is determined based on the predicted value of the attribute information of the current transform block.

[0230] In some embodiments, the decoding method further includes: decoding the bitstream to determine the residual value of the attribute information of the current transform block of the current transform layer.

[0231] Furthermore, in some embodiments, step 903 may include: determining the attribute information of the current transform block based on the residual value and the predicted value of the attribute information of the current transform block.

[0232] For an understanding of step 903 and further embodiments, please refer to the previous description of step 703 and further embodiments. To avoid repetition, they will not be repeated here.

[0233] In some embodiments, the decoding method further includes: when the current transform layer is a middle or upper layer of the current point cloud, decoding the bitstream to determine a fifth syntax element; determining the layer prediction mode of the current transform layer based on the fifth syntax element; wherein, when the current transform layer is a middle or upper layer, the layer prediction mode indicated by the fifth syntax element is any one of the fifth, sixth, and seventh layer prediction modes; determining the prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer. Subsequently, the attribute information of the current transform block of the current transform layer is determined according to steps 902 to 903.

[0234] In some embodiments, the decoding method further includes: when the current transform layer is above the current point cloud, decoding the bitstream to determine a seventh syntax element; determining the layer prediction mode of the current transform layer based on the seventh syntax element; wherein, when the current transform layer is above the current layer, the layer prediction mode indicated by the seventh syntax element is either the tenth layer prediction mode or the eleventh layer prediction mode; and determining the prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer. Subsequently, the attribute information of the current transform block of the current transform layer is determined according to steps 902 to 903.

[0235] As mentioned above, the current point cloud transformation layer is divided into upper, middle, and lower layers. Depending on the layer to which the current transformation layer belongs (e.g., upper, middle, or lower), this application provides corresponding decoding and encoding methods. For example, Embodiment 4 and its further or additional embodiments described below are encoding method embodiments for the current transformation layer belonging to the upper layer; Embodiment 5 and its further or additional embodiments described below are encoding method embodiments for the current transformation layer belonging to the upper-middle layer; and Embodiment 6 and its further or additional embodiments described below are encoding method embodiments for the current transformation layer belonging to the lowest layer. For the point cloud encoder, it can support decoding methods combining any one or more embodiments from Embodiment 4 and its further or additional embodiments, Embodiment 5 and its further or additional embodiments, and Embodiment 6 and its further or additional embodiments.

[0236] Example 4:

[0237] This application provides an encoding method that can be applied to a point cloud encoder. Figure 10 is a schematic diagram of the implementation flow of the encoding method provided in this application. As shown in Figure 10, the method includes the following steps 1001 to 1003:

[0238] Step 1001: When the current transformation layer is the upper layer of the current point cloud, determine the prediction mode of the current transformation block of the current transformation layer according to the predefined first-layer prediction mode of the upper layer; the first-layer prediction mode includes one or more prediction modes.

[0239] Step 1002: Determine the predicted values ​​of the attribute information of the current transform block based on the prediction mode of the current transform block;

[0240] Step 1003: Obtain the encoded bits based on the predicted values ​​of the attribute information of the current transform block, and write the encoded bits into the bit stream.

[0241] It is understood that, in the embodiments of this application, for the current transform layer that belongs to the upper layer of the current point cloud, its layer prediction mode is a predefined first layer prediction mode. The encoder can directly determine the prediction mode of the current transform block that belongs to the upper layer based on the first layer prediction mode, without the need for rate-distortion optimization. Thus, the layer prediction mode used by the decoder is determined from multiple layer prediction modes, and there is no need to indicate in the bitstream which layer prediction mode the upper layer current transform layer uses. In this way, the encoding efficiency is improved while saving bitstream overhead.

[0242] The following describes and illustrates further or additional embodiments of Embodiment 4.

[0243] In step 1001, if the current transformation layer is the upper layer of the current point cloud, the prediction mode of the current transformation block of the current transformation layer is determined according to the predefined first-layer prediction mode of the upper layer; the first-layer prediction mode includes one or more prediction modes.

[0244] In some embodiments, the first-layer prediction mode includes an inter-frame prediction mode, in which the inter-frame prediction mode takes precedence.

[0245] Furthermore, in some embodiments, the first-layer prediction mode further includes one or more of the following prediction modes:

[0246] Intra-frame prediction mode;

[0247] Unpredictable patterns;

[0248] Average forecast pattern.

[0249] For example, in some embodiments, in the first-level prediction mode, the priority of the prediction modes from high to low is as follows: inter-frame prediction mode, intra-frame prediction mode, and no prediction mode.

[0250] It should be noted that the description and understanding of step 1001 and related embodiments, as well as further implementations of these embodiments, can be understood by referring to the further implementations of step 701 and step 1001 in Embodiment 1 above, and will not be repeated here.

[0251] In step 1002, the predicted values ​​of the attribute information of the current transform block are determined according to the prediction mode of the current transform block.

[0252] In some embodiments, the attribute information of the current transform block can be understood as the attribute information of the attribute values ​​of the current transform block in the transform domain. For example, the attribute information of the current transform block includes the transform coefficients of the current transform block, which may be AC ​​coefficients or DC coefficients.

[0253] In one possible implementation, the attribute values ​​of the child nodes / sub-transform blocks of the current transform block can be predicted based on the prediction mode of the current transform block to obtain the predicted attribute values ​​of the child nodes / sub-transform blocks of the current transform block; then, the predicted attribute values ​​of the child nodes / sub-transform blocks of the current transform block are subjected to RAHT transformation to obtain the predicted values ​​of the AC coefficients and DC coefficients of the current transform block, which are the predicted values ​​of the transform coefficients of the current transform block.

[0254] In another possible implementation, the predicted values ​​of the transform coefficients of the current transform block can be determined directly in the transform domain. In the transform domain, the transform coefficients (such as AC coefficients) of the current transform block are predicted according to the prediction mode of the current transform block to obtain the predicted values ​​of the transform coefficients of the current transform block.

[0255] In step 1003, the encoded bits are obtained based on the predicted values ​​of the attribute information of the current transform block, and the encoded bits are written into the bit stream.

[0256] In some embodiments, step 1003 may include: determining the residual value of the attribute information of the current transform block based on the predicted value of the attribute information of the current transform block and the attribute information of the current transform block; encoding the residual value of the attribute information of the current transform block and writing the obtained encoded bits into the bit stream.

[0257] In some embodiments, the attribute information of the current transform block can be understood as the attribute information of the current transform block's attribute values ​​in the transform domain. For example, the attribute information of the current transform block includes the transform coefficients of the current transform block, which can be AC ​​coefficients or DC coefficients. The residual value of the attribute information of the current transform block includes the residual value of the AC coefficients of the current transform block, and the predicted value of the attribute information of the current transform block includes the predicted value of the AC coefficients of the current transform block. Encoding the residual value of the attribute information of the current transform block and writing the obtained encoded bits into the bitstream includes: quantizing the residual value of the AC coefficients of the current transform block, encoding the quantized residual value of the AC coefficients, and writing the obtained encoded bits into the bitstream.

[0258] In one possible implementation, the AC coefficients of the current transform block can be subtracted from the predicted values ​​of the AC coefficients of the current transform block to obtain the residual values ​​of the AC coefficients of the current transform block. These residual values ​​are then quantized and entropy-coded to obtain coded bits, which are then written into the bitstream. Alternatively, in some embodiments, the residual value may not be quantized; instead, it may be directly written into the bitstream via entropy coding.

[0259] In some embodiments, the encoding method further includes: when the current transform layer is a middle or upper layer of the current point cloud, determining the layer prediction mode of the current transform layer based on the fifth layer prediction mode, the sixth layer prediction mode, and the seventh layer prediction mode; and determining the prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer. Subsequent steps are the same as steps 1002 and 1003.

[0260] In some embodiments, the encoding method further includes: when the current transform layer is a middle or upper layer of the current point cloud, determining the value of the fifth syntax element according to the layer prediction mode of the current transform layer; encoding the value of the fifth syntax element and writing the obtained encoded bits into the bitstream.

[0261] In one possible implementation, the corresponding rate-distortion costs obtained by using the fifth, sixth, and seventh prediction modes at the current transform layer can be determined, and the prediction mode with the lowest rate-distortion cost can be selected as the prediction mode for the current transform layer. The value of the fifth syntax element indicates the prediction mode with the lowest rate-distortion cost among the fifth, sixth, and seventh prediction modes.

[0262] In some embodiments, the encoding method further includes: when the current transform layer is the lowest layer of the current point cloud, determining the layer prediction mode of the current transform layer based on the prediction modes of the eighth and ninth layers; and determining the prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer. Subsequent steps are the same as steps 1002 and 1003.

[0263] In some embodiments, the encoding method further includes: when the current transform layer is the lowest layer of the current point cloud, determining the value of the sixth syntax element according to the layer prediction mode of the current transform layer; encoding the value of the sixth syntax element and writing the obtained encoded bits into the bitstream.

[0264] In one possible implementation, the corresponding rate-distortion costs obtained by using the eighth and ninth prediction modes at the current transform layer can be determined, and the prediction mode with the lowest rate-distortion cost can be selected as the prediction mode for the current transform layer. The value of the sixth syntax element indicates the prediction mode with the lowest rate-distortion cost between the eighth and ninth prediction modes.

[0265] Example 5:

[0266] This application provides an encoding method that can be applied to a point cloud encoder. Figure 11 is a schematic diagram of the implementation flow of the encoding method provided in this application. As shown in Figure 11, the method includes the following steps 1101 to 1104:

[0267] Step 1101: If the current transformation layer is the middle or upper layer of the current point cloud, determine the layer prediction mode of the current transformation layer based on the second layer prediction mode and the third layer prediction mode.

[0268] Step 1102: Determine the prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer;

[0269] Step 1103: Determine the predicted values ​​of the attribute information of the current transform block based on the prediction mode of the current transform block;

[0270] Step 1104: Obtain the encoded bits based on the predicted values ​​of the attribute information of the current transform block, and write the encoded bits into the bit stream.

[0271] The following describes and illustrates further or additional embodiments of Embodiment 5.

[0272] In step 1101, if the current transformation layer is a middle or upper layer of the current point cloud, the layer prediction mode of the current transformation layer is determined.

[0273] In some embodiments, the upper-middle layer of the current point cloud refers to the transformation layer in the middle layer of the current point cloud and close to the root node. In the embodiments of this application, the method for determining whether the current transformation layer is the upper-middle layer of the current point cloud is not limited.

[0274] The encoder can determine whether the current transform layer belongs to the upper-middle layer by calculation. In one possible implementation, a maximum number of layers parameter is added to the APS, whose value can be a predefined value, for example, 3.

[0275] aps.rahtPredParams.upper_in_middle_mode_level,3

[0276] Subsequently, an inference procedure was added to the codec, as follows:

[0277] First, create a boolean variable `upperInMiddleLevel`, with a value of 1 indicating that it is in the upper middle level, and otherwise not in the upper middle level.

[0278] The program then infers that: the distance of the current transformation layer from the root node is greater than the number of upper layers and less than (the number of upper layers + half the number of middle layers); additionally, the number of upper-middle layers is less than the corresponding maximum preset value. If the above conditions are met, then `upperInMiddleLevel` is inferred to be 1, meaning the current transformation layer is an upper-middle layer. For example, the following computer program can be used to determine whether the current transformation layer is an upper-middle layer: `bool upperInMiddleLevel = distanceToRoot >= rahtPredParams.upper_mode_level`

[0279] &&distanceToRoot

[0280] <layerDepth-(layerDepth-rahtPredParams.upper_mode_level) / 2

[0281] &&! upperInferMode&&! realInferInLowerLevel&&distanceToRoot <rahtPredParams.upper_mode_level+rahtPredParams.upper_in_middle_mode_level;

[0282] In other embodiments, after the encoder obtains the result that the current transform layer belongs to the upper-middle layer, it determines the value of the third syntax element based on this result; and encodes the value of the third syntax element and writes the obtained encoded bits into the bit stream; wherein the value of the third syntax element is equal to the first value, indicating that the current transform layer is in the upper-middle layer of the middle layer.

[0283] In step 1101, if the current transformation layer is a middle or upper layer of the current point cloud, the layer prediction mode of the current transformation layer is determined based on the second layer prediction mode and the third layer prediction mode.

[0284] In some embodiments, the encoding method further includes: when the current transform layer is a middle or upper layer of the current point cloud, determining the value of the first syntax element according to the layer prediction mode of the current transform layer; encoding the value of the first syntax element and writing the obtained encoded bits into the bitstream.

[0285] In one possible implementation, the rate-distortion cost obtained by using the second-layer prediction mode at the current transform layer and the rate-distortion cost obtained by using the third-layer prediction mode at the current transform layer can be determined, and the value of the first syntax element indicates the layer prediction mode with the minimum rate-distortion cost among the second-layer and third-layer prediction modes.

[0286] It is understood that in the encoding method provided in this application embodiment, for the current transform layer belonging to the upper-middle layer of the current point cloud, its layer prediction mode is indicated by the first syntax element. The first syntax element indicates either the second layer prediction mode or the third layer prediction mode. Therefore, the first syntax element can indicate the layer prediction mode of the upper-middle layer using only one bit, without needing to use two or more bits to indicate the layer prediction mode of the upper-middle layer; thus, it is beneficial to save bitstream overhead. On the other hand, at the encoding end, the encoder only needs to determine the rate-distortion cost corresponding to the second layer prediction mode and the third layer prediction mode corresponding to the current transform layer, without needing to determine the rate-distortion cost of the third layer prediction mode, thus saving the time overhead caused by calculating the rate-distortion cost, thereby improving encoding efficiency.

[0287] In some embodiments, the encoding method further includes: encoding the value of the first syntax element and writing the resulting encoded bits into the bitstream.

[0288] In some embodiments, the second-layer prediction mode includes an inter-frame prediction mode, in which the inter-frame prediction mode takes precedence.

[0289] Furthermore, in some embodiments, the second-layer prediction mode further includes one or more of the following prediction modes:

[0290] Intra-frame prediction mode;

[0291] Unpredictable patterns;

[0292] Average forecast pattern.

[0293] For example, in some embodiments, in the second-layer prediction mode, the priority of the prediction modes from high to low is as follows: inter-frame prediction mode, intra-frame prediction mode, and no prediction mode.

[0294] In some embodiments, the third-layer prediction mode includes one or more prediction modes. Further, in some embodiments, the third-layer prediction mode includes one or more of the following prediction modes:

[0295] Inter-frame prediction mode;

[0296] Intra-frame prediction mode;

[0297] Unpredictable patterns;

[0298] Average forecast pattern.

[0299] For example, in some embodiments, the third-layer prediction modes include inter-frame prediction mode, intra-frame prediction mode, and no prediction mode.

[0300] In some embodiments, the encoding method further includes: determining the value of a second syntax element when the layer prediction mode of the current transform layer is the third layer prediction mode; and encoding the value of the second syntax element and writing the obtained encoded bits into the bitstream; wherein the value of the second syntax element is used to indicate the prediction mode of the current transform block of the current transform layer.

[0301] In one possible implementation, for the encoder, when the value of the first syntax element indicates the third-level prediction mode, the encoder can determine the rate-distortion cost obtained by the current transform block using multiple prediction modes respectively, and take the prediction mode with the lowest rate-distortion cost as the prediction mode of the current transform block. The value of the second syntax element indicates the prediction mode with the lowest rate-distortion cost.

[0302] In some embodiments, the encoding method further includes: when the current transform layer is above the current point cloud, determining the layer prediction mode of the current transform layer based on the prediction modes of the tenth and eleventh layers. Subsequent steps are the same as steps 1102 to 1104.

[0303] In some embodiments, the encoding method further includes: when the current transform layer is the upper layer of the current point cloud, determining the value of the seventh syntax element according to the layer prediction mode of the current transform layer; encoding the value of the seventh syntax element and writing the obtained encoded bits into the bitstream.

[0304] In one possible implementation, the corresponding rate-distortion costs obtained by using the tenth-level prediction mode and the eleventh-level prediction mode at the current transform layer can be determined, and the prediction mode with the lowest rate-distortion cost can be selected as the prediction mode for the current transform layer. The value of the seventh syntax element indicates the prediction mode with the lowest rate-distortion cost between the tenth-level and eleventh-level prediction modes.

[0305] In some embodiments, the encoding method further includes: when the current transform layer is the lowest layer of the current point cloud, determining the layer prediction mode of the current transform layer based on the eighth layer prediction mode and the ninth layer prediction mode. Subsequent steps are the same as steps 1102 to 1104.

[0306] In some embodiments, the encoding method further includes: when the current transform layer is the lowest layer of the current point cloud, determining the value of the sixth syntax element according to the layer prediction mode of the current transform layer; encoding the value of the sixth syntax element and writing the obtained encoded bits into the bitstream.

[0307] In one possible implementation, the corresponding rate-distortion costs obtained by using the eighth and ninth prediction modes at the current transform layer can be determined, and the prediction mode with the lowest rate-distortion cost can be selected as the prediction mode for the current transform layer. The value of the sixth syntax element indicates the prediction mode with the lowest rate-distortion cost between the eighth and ninth prediction modes.

[0308] In step 1104, the encoded bits are obtained based on the predicted values ​​of the attribute information of the current transform block, and the encoded bits are written into the bit stream.

[0309] In some embodiments, step 1104 may include: determining the residual value of the attribute information of the current transform block based on the predicted value of the attribute information of the current transform block and the attribute information of the current transform block; and encoding the residual value of the attribute information of the current transform block and writing the obtained encoded bits into the bit stream.

[0310] In some embodiments, the attribute information of the current transform block can be understood as the attribute information of the current transform block's attribute values ​​in the transform domain. For example, the attribute information of the current transform block includes the transform coefficients of the current transform block, which can be AC ​​coefficients or DC coefficients. The residual value of the attribute information of the current transform block includes the residual value of the AC coefficients of the current transform block, and the predicted value of the attribute information of the current transform block includes the predicted value of the AC coefficients of the current transform block.

[0311] The residual values ​​of the attribute information of the current transform block are encoded, and the resulting encoded bits are written into the bitstream, including:

[0312] The residual values ​​of the AC coefficients of the current transform block are quantized, the quantized residual values ​​of the AC coefficients are encoded, and the resulting encoded bits are written into the bitstream.

[0313] In one possible implementation, the AC coefficients of the current transform block can be subtracted from the predicted values ​​of the AC coefficients of the current transform block to obtain the residual values ​​of the AC coefficients of the current transform block. These residual values ​​are then quantized and entropy-coded to obtain coded bits, which are then written into the bitstream. Alternatively, in some embodiments, the residual value may not be quantized; instead, it may be directly written into the bitstream via entropy coding.

[0314] Example 6:

[0315] This application provides an encoding method that can be applied to a point cloud encoder. Figure 12 is a schematic diagram of the implementation flow of the encoding method provided in this application. As shown in Figure 12, the method includes the following steps 1201 to 1203:

[0316] Step 1201: When the current transformation layer is the lowest layer of the current point cloud, determine the prediction mode of the current transformation block of the current transformation layer according to the predefined fourth layer prediction mode of the lowest layer; the fourth layer prediction mode includes one or more prediction modes.

[0317] Step 1202: Determine the predicted values ​​of the attribute information of the current transform block based on the prediction mode of the current transform block;

[0318] Step 1203: Obtain the encoded bits based on the predicted values ​​of the attribute information of the current transform block, and write the encoded bits into the bit stream.

[0319] It is understood that, in the embodiments of this application, for the current transform layer that is the lowest layer of the current point cloud, its layer prediction mode is the predefined fourth layer prediction mode. The encoder can directly determine the prediction mode of the current transform block that belongs to the lowest layer of the current transform layer based on the fourth layer prediction mode, without the need for rate-distortion optimization. Thus, the layer prediction mode used by the decoder is determined from multiple layer prediction modes, and there is no need to indicate in the bitstream which layer prediction mode is used for the lowest layer of the current transform layer. In this way, the encoding efficiency is improved while saving bitstream overhead.

[0320] The following describes and illustrates further or additional embodiments of Embodiment Six.

[0321] In step 1201, if the current transformation layer is the lowest layer of the current point cloud, the prediction mode of the current transformation block of the current transformation layer is determined according to the predefined fourth-layer prediction mode of the lowest layer; the fourth-layer prediction mode includes one or more prediction modes.

[0322] In some embodiments, the lowest layer of the current point cloud can be one or more transformation layers among the lower layers of the current point cloud. Exemplarily, in some embodiments, the lowest layer of the current point cloud refers to the transformation layer containing the leaf nodes of the current point cloud and / or the transformation layer closest to the leaf nodes. For example, the lowest layer of the current point cloud may be a layer with average prediction disabled.

[0323] In this embodiment, the method for determining whether the current transform layer is the lowest layer of the current point cloud is not limited. The layer to which the current point cloud belongs is determined by calculation. In other embodiments, the current transform layer may also be indicated as the lowest layer in the bitstream using a fourth syntax element.

[0324] In this embodiment, there is no limitation on the fourth-layer prediction mode, which is a layer prediction mode that includes one or more prediction modes. In summary, for the current transform layer that is the lowest layer, the prediction mode of its current transform block is determined based on the predefined fourth-layer prediction mode.

[0325] In some embodiments, the fourth-layer prediction mode includes an intra-frame prediction mode, in which the intra-frame prediction mode takes precedence.

[0326] This is understandable. The so-called "intra-prediction mode priority" means that when determining the prediction mode of the current transform block in the current transform layer, it is prioritized to determine whether an intra-prediction mode can be used. For example, in some embodiments, the fourth-layer prediction modes include an intra-prediction mode and a no-prediction mode, with the intra-prediction mode having a higher priority than the no-prediction mode. That is, in the fourth-layer prediction modes, Intra > Null. Therefore, it is prioritized to determine whether the intra-predicted value is not 0; if it is not 0, the intra-prediction mode is used; otherwise, the no-prediction mode is used.

[0327] It should be noted that, through analysis, it was found that for the RAHT transform layers of point clouds, the transform block level is at or near the voxel level in the transform layers near the leaf nodes. Therefore, for the leaf node layer (i.e., the transform layer where the leaf node is located) and / or the transform layer near the leaf node layer, the attribute values ​​of transform blocks at the same level differ significantly between adjacent frames. If the predicted value of the attribute information of the transform block is determined using the inter-frame prediction mode within the leaf node layer or the transform layer near the leaf node layer, the prediction accuracy is low, resulting in a large bit overhead for the residual value written to the bitstream. In view of this, in the embodiments of this application, for the transform layer belonging to the bottom layer of the current point cloud, its possible layer prediction modes do not include the layer prediction mode that prioritizes the inter-frame prediction mode. For the transform layer belonging to the bottom layer of the current point cloud, its layer prediction mode is the layer prediction mode that prioritizes the intra-frame prediction mode; thus, for the encoder, there is no need to perform rate-distortion optimization to select the layer prediction mode used by the decoder, and correspondingly, there is no need to indicate the layer prediction mode used by the current transform layer in the bitstream. Thus, it is possible to save bitstream overhead and improve the coding efficiency of the current point cloud without sacrificing the prediction accuracy of the current transform block.

[0328] In step 1202, the predicted values ​​of the attribute information of the current transform block are determined according to the prediction mode of the current transform block.

[0329] For an understanding of step 1202 and further embodiments, please refer to the previous description of step 702 and further embodiments. To avoid repetition, they will not be repeated here.

[0330] In some embodiments, the encoding method further includes: when the current transform layer is a middle or upper layer of the current point cloud, determining the layer prediction mode of the current transform layer based on the fifth layer prediction mode, the sixth layer prediction mode, and the seventh layer prediction mode; and determining the prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer. Subsequent steps are the same as steps 1202 and 1203.

[0331] In some embodiments, the encoding method further includes: when the current transform layer is a middle or upper layer of the current point cloud, determining the value of the fifth syntax element according to the layer prediction mode of the current transform layer; encoding the value of the fifth syntax element and writing the obtained encoded bits into the bitstream.

[0332] In one possible implementation, the corresponding rate-distortion costs obtained by using the fifth, sixth, and seventh prediction modes at the current transform layer can be determined, and the prediction mode with the lowest rate-distortion cost can be selected as the prediction mode for the current transform layer. The value of the fifth syntax element indicates the prediction mode with the lowest rate-distortion cost among the fifth, sixth, and seventh prediction modes.

[0333] In some embodiments, the encoding method further includes: when the current transform layer is above the current point cloud, determining the layer prediction mode of the current transform layer based on the prediction modes of the tenth and eleventh layers; and determining the prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer. Subsequent steps are the same as steps 1202 and 1203.

[0334] In some embodiments, the encoding method further includes: when the current transform layer is the upper layer of the current point cloud, determining the value of the seventh syntax element according to the layer prediction mode of the current transform layer; encoding the value of the seventh syntax element and writing the obtained encoded bits into the bitstream.

[0335] In one possible implementation, the corresponding rate-distortion costs obtained by using the tenth-level prediction mode and the eleventh-level prediction mode at the current transform layer can be determined, and the prediction mode with the lowest rate-distortion cost can be selected as the prediction mode for the current transform layer. The value of the seventh syntax element indicates the prediction mode with the lowest rate-distortion cost between the tenth-level and eleventh-level prediction modes.

[0336] Step 1203: Obtain the encoded bits based on the predicted values ​​of the attribute information of the current transform block, and write the encoded bits into the bit stream.

[0337] In some embodiments, step 1203 may include: determining the residual value of the attribute information of the current transform block based on the predicted value of the attribute information of the current transform block and the attribute information of the current transform block; and encoding the residual value of the attribute information of the current transform block and writing the obtained encoded bits into the bit stream.

[0338] In some embodiments, the attribute information of the current transform block can be understood as the attribute information of the current transform block's attribute values ​​in the transform domain. For example, the attribute information of the current transform block includes the transform coefficients of the current transform block, which can be AC ​​coefficients or DC coefficients. The residual value of the attribute information of the current transform block includes the residual value of the AC coefficients of the current transform block, and the predicted value of the attribute information of the current transform block includes the predicted value of the AC coefficients of the current transform block. Encoding the residual value of the attribute information of the current transform block and writing the obtained encoded bits into the bitstream includes: quantizing the residual value of the AC coefficients of the current transform block, encoding the quantized residual value of the AC coefficients, and writing the obtained encoded bits into the bitstream.

[0339] In one possible implementation, the AC coefficients of the current transform block can be subtracted from the predicted values ​​of the AC coefficients of the current transform block to obtain the residual values ​​of the AC coefficients of the current transform block. These residual values ​​are then quantized and entropy-coded to obtain coded bits, which are then written into the bitstream. Alternatively, in some embodiments, the residual value may not be quantized; instead, it may be directly written into the bitstream via entropy coding.

[0340] It should also be noted that the encoding method described in Embodiment 4 and its further or additional embodiments is different from the decoding method described in Embodiment 1 and its further or additional embodiments. Therefore, for any technical details not disclosed in Embodiment 4 and its further or additional embodiments, please refer to the corresponding descriptions and explanations in Embodiment 1 and its further or additional embodiments for understanding.

[0341] The encoding method described in Embodiment 5 and its further or additional embodiments is the same as the decoding method described in Embodiment 2 and its further or additional embodiments. Therefore, for any technical details not disclosed in Embodiment 5 and its further or additional embodiments, please refer to the corresponding descriptions and explanations in Embodiment 2 and its further or additional embodiments for understanding.

[0342] The encoding method described in Embodiment Six and its further or additional embodiments is the same as the decoding method described in Embodiment Three and its further or additional embodiments. Therefore, for any technical details not disclosed in Embodiment Six and its further or additional embodiments, please refer to the corresponding descriptions and explanations in Embodiment Three and its further or additional embodiments for understanding.

[0343] To save space and avoid repetition, some technical details regarding the coding method will not be explained or described here.

[0344] It should also be noted that the syntax elements used to indicate the layer prediction mode of the current transform layer, such as the first syntax element, the fifth syntax element, the sixth syntax element, the seventh syntax element, etc. mentioned in this article, can be the same syntax element (such as predMode). For different layer prediction modes (for example, the different layer prediction modes can refer to two or three layer prediction modes among OrgCodingMethod, Inter-layerCodingMethod, and Intra-layerCodingMethod), the value of this syntax element is different. For different transform layers, the encoding method of the value of this syntax element may also be different.

[0345] The following describes possible implementations of the encoding / decoding methods described in one or more of the above embodiments.

[0346] In this application embodiment, a coding structure optimization scheme for RAHT layer prediction modes is provided.

[0347] Analysis revealed that during the RAHT algorithm's layer-by-layer computation from the root node to the leaf node, within each layer of the transform, rate-distortion optimization is first used to select the optimal prediction mode from three layer prediction modes: OrgCodingMethod, Inter-layerCodingMethod, and Intra-layerCodingMethod. Then, based on Table 1 mentioned earlier, the AC prediction method (inter-frame prediction / intra-frame prediction / average prediction / no prediction) for the transform block within the layer is determined. However, for multi-frame dynamic point clouds, in the upper layers near the root node in the RAHT transform, the attribute values ​​within larger transform blocks show almost zero change between adjacent frames. Therefore, the inter-frame prediction values ​​of the AC coefficients in the upper layers near the root node are necessarily relatively accurate. Consequently, the priority intra-frame prediction scheme in the Intra-layerCodingMethod prediction mode is unreasonable.

[0348] In view of this, this application proposes an optimization of the encoding and decoding structure for the layer RDO prediction mode, targeting the optimal prediction mode selection scheme for each layer, and addressing the irrationality of the Intra-layerCodingMethod prediction mode in the upper layers near the root node. This application proposes two solutions. One is to remove the Intra-layerCodingMethod prediction mode from the currently defined upper layers (the three layers near the root node). Therefore, in the upper layers of the RAHT transform, only OrgCodingMethod works, and the encoder does not need to encode the prediction mode of this layer. Details of the improved layer-optimal prediction mode are shown in Table 5.

[0349] Table 5. Details of the optimal prediction model for the RAHT layer.

[0350] This application also proposes an improved scheme 2, which further increases the depth by removing the Intra-layer CodingMethod prediction mode. First, a marker named upperInMiddleLevel is added within the middle layer to indicate the level closest to the root node. A value of 1 indicates a level slightly above the middle layer, i.e., an upper-middle layer. The number of upperInMiddleLevel layers is half the total number of middle layers (rounded down). Therefore, within the upperInMiddleLevel layer, the Intra-layer CodingMethod prediction mode is removed, leaving only OrgCodingMethod and Inter-layer CodingMethod prediction modes. For encoding these layer prediction modes, the encoder uses 1 bit of 0 / 1 encoding. Details of the optimal prediction mode for the improved layer are shown in Table 6. The combined improved scheme is also shown in Table 6.

[0351] Table 6. Details of the Optimal Prediction Mode for the RAHT Layer

[0352] Table 7. Details of the Optimal Prediction Mode for the RAHT Layer

[0353] The implementation details of the encoding and decoding ends are described below.

[0354] (1) Implementation details of the encoding end:

[0355] In the RAHT algorithm, the original point cloud starts from the root node and undergoes a layer-by-layer RAHT transformation for each 2×2×2 block from top to bottom to obtain transformation coefficients. For each layer, AC coefficient prediction is performed. First, three layer prediction modes—OrgCodingMethod, Inter-layerCodingMethod, and Intra-layerCodingMethod—are considered. The optimal layer prediction mode is obtained using layer RDO, and then the optimal prediction residual is obtained. However, for multi-frame dynamic point clouds, in the upper layers near the root node during the RAHT transformation, the attribute values ​​within larger transformation blocks change almost zero between adjacent frames. Therefore, the inter-frame prediction values ​​of AC coefficients in the upper layers near the root node are relatively accurate, making the priority intra-frame prediction scheme in the Intra-layerCodingMethod prediction mode unreasonable. To address this issue, we first set `upperInMiddleLevel` to indicate the layers near the root node in the middle layers; a value of 1 indicates a layer slightly above the middle layer. Subsequently, in the upper and upper-middle levels, the Intra-layer CodingMethod is removed, and the optimal prediction mode (inter-frame prediction / intra-frame prediction / average prediction / no prediction) is selected according to the new layer optimal prediction mode details table (as shown in Tables 4 to 6). The residual value is quantized, and then the quantized residual value is encoded. When encoding the predMode of each layer, the upper layer is changed from encoding the original two modes, OrgCodingMethod and Inter-layerCodingMethod, to encoding only one prediction mode, OrgCodingMethod, so there is no need to encode the predMode of the upper layer; in upperInMiddleLevel, the original three modes of encoding 0,01,11 are changed to encoding 0,1 for OrgCodingMethod and Inter-layerCodingMethod, thus saving the overhead of encoding bits. The operation flow at the encoding end is shown in Figure 13. For the current transform layer belonging to the upper level or upperInMiddlelevel, the candidate layer prediction mode, Intra-layerCodingMethod, is removed. Based on the prediction modes of the remaining layers, the prediction residual of the AC coefficients of the current transform block of the current transform layer is determined, the prediction residual is quantized, and the quantized prediction residual is encoded. Furthermore, for the current transform layer in the upper middle layer, the predMode of the layer also needs to be encoded to indicate whether the layer prediction mode of the layer is OrgCodingMethod or Inter-layerCodingMethod.

[0356] It should be noted that the term "middle-to-upper layer" in this application can also be understood as "middle-upper layer".

[0357] The program operation at the encoding end changes as follows: The definition of the upperInMiddleLevel level is added. In the upper layer (upperInferMode), the encoder no longer performs entropy encoding; in the upperInMiddleLevel level, the encoder only needs one bit for encoding.

[0358] In this embodiment, a definition of upper-middle level is added to indicate the upper part of the middle level. First, a maximum number of levels parameter is added to the APS, and its value is defined as 3.

[0359] aps.rahtPredParams.upper_in_middle_mode_level,3

[0360] Subsequently, an inference procedure was added to the codec, as follows:

[0361] First, create a boolean variable `upperInMiddleLevel`, with a value of 1 indicating that it is in the upper middle level, and otherwise not in the upper middle level.

[0362] The program then infers that: the distance from the root node is greater than the number of upper-level nodes and less than (the number of upper-level nodes plus half the number of middle-level nodes); additionally, the number of upper-middle-level nodes is less than the defined maximum preset value. If these conditions are met, the inference is 1.

[0363] (2) Bitstream structure:

[0364] The bitstream structure of the relevant technology is shown in Figure 14. It can be seen that in the predMode bitstream structure, two bits, ctxLayerPred and ctxInterLayerPred, are used to encode different layer prediction modes. In the upper and lower layers (in the last layer where average prediction is disabled), the encoder only uses one bit of ctxLayerPred (0 / 1) to indicate two encoding modes / layer prediction modes. In the remaining layers, the encoder uses two bits, ctxLayerPred and ctxInterLayerPred, to indicate three encoding modes (0 / 01 / 11), as detailed in Table 1.

[0365] The bitstream structure corresponding to the embodiment of this application is shown in Figure 15. It can be seen that, compared with Figure 14, in the improved predMode bitstream structure shown in Figure 15, since the Intra-layerCodingMethod is removed in the upper layer, there is no need to encode the layer prediction mode anymore. In the upper middle layer, the encoder uses one bit (0 / 1) of ctxLayerPred to replace the two bits (0 / 01 / 11) of ctxLayerPred and ctxInterLayerPred for encoding, and the encoding of the other layers remains unchanged. Details are shown in Tables 4 to 6.

[0366] (3) Decoding implementation details:

[0367] The decoding process is illustrated in Figure 16. RAHT decoding still proceeds layer by layer from the root node to the leaf node. The decoder reads the bitstream and first decodes the optimal prediction index `predMode` for each layer. If it's in an upper layer, decoding `predMode` is unnecessary; if it's in a middle or upper layer, only one bit of `ctxLayerPred` needs to be decoded to determine whether the prediction mode is `OrgCodingMethod` or `Inter-layerCodingMethod`. The remaining layers are decoded using the original method. Based on the decoded prediction mode `predMode`, the prediction mode of each node (inter-frame prediction / average prediction / intra-frame prediction / no prediction) can be determined, allowing the calculation of the predicted AC coefficients for each layer.

[0368] The decoded values ​​are dequantized to obtain the reconstructed AC coefficient residuals. These residuals are added to the predicted values ​​to obtain the reconstructed AC coefficients for each layer. The decoding process continues from top to bottom. First, the DC coefficients of the root node and the AC coefficients of the first layer are obtained, and an inverse RAHT transform is performed to obtain the reconstructed attribute values. The obtained 8 reconstructed attribute values ​​can be used to calculate the DC coefficients of the 8 nodes in the second layer. Then, an inverse RAHT transform is performed with the reconstructed AC coefficients of the second layer to obtain the reconstructed attribute values ​​of the third layer, and so on, until all point cloud attributes are reconstructed.

[0369] In this embodiment, the decoding program is implemented as follows: in the upperInferMode, no decoding is required, and the prediction mode 0 is returned directly. Then, the first bit ctxLayerPred is decoded, and the layer prediction mode is inferred based on the layer position. For a layer with three layer prediction modes and the first bit ctxLayerPred is decoded as 1, the decoder needs to continue decoding the second bit ctxInterLayerPred to find out the specific layer prediction mode.

[0370] The technical solution provided in this application was implemented on the G-PCC reference software Ges-TM V6.0-rc1 and tested under CTC test conditions (C1, C2, and CW). Test results show that, compared to the original solution, the technical solution provided in this application reduces the bitrate to a certain extent under both Ges-TM and CTC test conditions, while maintaining the same PSNR. Furthermore, it also reduces the time complexity of encoding and decoding to a certain extent.

[0371] It is understood that, in the embodiments of this application, an optimization scheme for the encoding and decoding structure under the RAHT layer prediction mode is provided, which effectively solves the problem of the unreasonable use of the Intra-layer CodingMethod prediction mode with priority intra-frame prediction in the upper layer near the root node in the RAHT transform for multi-frame dynamic point clouds.

[0372] In other embodiments, an upperInMiddleLevel layer marker is added, the Intra-layerCodingMethod is removed in the upper layer, and the prediction mode index is no longer encoded; in the middle and upper layers, the Intra-layerCodingMethod is removed and one bit encoding is used instead of two bits, thereby reducing the code rate and improving the encoding performance.

[0373] Furthermore, analysis revealed that in the RAHT transform, at the lowest level (the last layer) near the leaf nodes, the transform block level is only voxel-level. Therefore, for transform blocks in the leaf node layer, the inter-block attribute values ​​differ significantly between adjacent frames. Consequently, the inter-frame prediction accuracy of AC coefficients within the leaf node layer is very low, making the use of the pre-layerCodingMethod prediction mode unreasonable. Therefore, the Inter-layerCodingMethod can be removed at this level, eliminating the need to encode predMode, as shown in Table 8 below.

[0374] Table 8. Details of the Optimal Prediction Mode for the RAHT Layer

[0375] It should be noted that, in the embodiments of this application, for the current transform layer encoding and decoding method, the RAHT layer optimal prediction mode detail table used by the encoder and decoder can be any detail table in Table 2, Table 3 and Table 4, or a combination of any two detail tables in Table 2, Table 3 and Table 4, or a combination of Table 2, Table 3 and Table 4.

[0376] The detailed table after combining Tables 2 and 3 is shown in Table 7 above. The detailed table after combining Tables 2 and 4 is shown in Table 9 below. The detailed table after combining Tables 3 and 4 is shown in Table 10 below. The detailed table after combining Tables 2, 3 and 4 is shown in Table 11 below.

[0377] Table 9. Details of the Optimal Prediction Model for the RAHT Layer

[0378] Table 10 Detailed Table of Optimal Prediction Models for RAHT Layer

[0379] Table 11 Detailed Table of Optimal Prediction Modes for RAHT Layer

[0380] It should be noted that although the steps of the method in this application are described in a specific order in the accompanying drawings, this does not require or imply that the steps must be performed in that specific order, or that all the steps shown must be performed to achieve the desired result. Additional or alternative steps may be omitted, multiple steps may be combined into one step, and / or one step may be broken down into multiple steps; or steps from different embodiments may be combined into a new technical solution.

[0381] Based on the foregoing embodiments, this application provides a decoding device applied to a point cloud decoder. Figure 17 is a schematic diagram of the structure of the decoding device provided in this application. As shown in Figure 17, the decoding device 170 includes:

[0382] The first determining module 1701 is configured to determine the prediction mode of the current transform block of the current transform layer based on the predefined first-layer prediction mode of the upper layer when the current transform layer is the upper layer of the current point cloud; the first-layer prediction mode includes one or more prediction modes.

[0383] The second determining module 1702 is configured to determine the predicted value of the attribute information of the current transform block based on the prediction mode of the current transform block.

[0384] The third determining module 1703 is configured to determine the attribute information of the current transform block based on the predicted value of the attribute information of the current transform block.

[0385] In some embodiments, the decoding device 170 further includes a decoding module, which is configured to decode the bitstream and determine a first syntax element when the current transform layer is a middle or upper layer of the current point cloud; the first determining module 1701 is further configured to determine the layer prediction mode of the current transform layer based on the first syntax element; and determine the prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer.

[0386] In some embodiments, when the current transform layer is a middle or upper layer of the current point cloud, the layer prediction mode indicated by the first syntax element is either the second layer prediction mode or the third layer prediction mode.

[0387] In some embodiments, the first determining module 1701 is further configured to determine the prediction mode of the current transform block of the current transform layer according to the predefined fourth-layer prediction mode of the lowest layer when the current transform layer is the lowest layer of the current point cloud; the fourth-layer prediction mode includes one or more prediction modes.

[0388] In some embodiments, the fourth-layer prediction mode includes an intra-frame prediction mode, in which the intra-frame prediction mode takes precedence.

[0389] For example, in some embodiments, the fourth-layer prediction mode includes an intra-frame prediction mode and a no-prediction mode, with the intra-frame prediction mode having a higher priority than the no-prediction mode.

[0390] In some embodiments, the first-layer prediction mode includes an inter-frame prediction mode, and / or, the second-layer prediction mode includes an inter-frame prediction mode; in the first-layer prediction mode, and / or, in the second-layer prediction mode, the inter-frame prediction mode takes precedence.

[0391] Furthermore, the first-layer prediction model also includes one or more of the following prediction models, and / or the second-layer prediction model also includes one or more of the following prediction models:

[0392] Intra-frame prediction mode;

[0393] Unpredictable patterns;

[0394] Average forecast pattern.

[0395] For example, in some embodiments, in the first-layer prediction mode and / or in the second-layer prediction mode, the prediction modes are prioritized from high to low as follows: inter-frame prediction mode, intra-frame prediction mode, and no prediction mode.

[0396] In some embodiments, the third-layer prediction model includes one or more prediction models.

[0397] Furthermore, in some embodiments, the third-layer prediction mode includes one or more of the following prediction modes:

[0398] Inter-frame prediction mode;

[0399] Intra-frame prediction mode;

[0400] Unpredictable patterns;

[0401] Average forecast pattern.

[0402] Further, in some embodiments, determining the prediction mode of the current transform block of the current transform layer according to the layer prediction mode of the upper-middle layer indicated by the first syntax element includes: if the layer prediction mode indicated by the first syntax element is the third layer prediction mode, decoding the bitstream to determine the second syntax element; and determining the prediction mode of the current transform block according to the value of the second syntax element; wherein the second syntax element is used to indicate the prediction mode of the current transform block of the current transform layer.

[0403] In some embodiments, the decoding device 170 further includes a decoding module configured to decode the bitstream and determine a third syntax element; wherein the third syntax element is used to indicate the position of the current transform layer in the middle layer; wherein the value of the third syntax element is equal to a first value, indicating that the current transform layer is in the upper-middle layer of the middle layer.

[0404] In some embodiments, the decoding device 170 further includes a decoding module configured to decode the bitstream and determine a fifth syntax element when the current transform layer is a middle or upper layer of the current point cloud; the first determining module 1701 is further configured to determine the layer prediction mode of the current transform layer based on the fifth syntax element; wherein, when the current transform layer is a middle or upper layer, the layer prediction mode indicated by the fifth syntax element is any one of the fifth layer prediction mode, the sixth layer prediction mode, and the seventh layer prediction mode; and to determine the prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer.

[0405] In some embodiments, the decoding device 170 further includes a decoding module configured to decode the bitstream and determine a sixth syntax element when the current transform layer is the lowest layer of the current point cloud; the first determining module 1701 is further configured to determine the layer prediction mode of the current transform layer based on the sixth syntax element; wherein, when the current transform layer is the lowest layer, the layer prediction mode indicated by the sixth syntax element is either the eighth layer prediction mode or the ninth layer prediction mode; and to determine the prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer.

[0406] In some embodiments, the decoding device 170 further includes a decoding module configured to decode the bitstream and determine the residual value of the attribute information of the current transform block of the current transform layer.

[0407] In some embodiments, determining the attribute information of the current transform block based on the predicted value of the attribute information of the current transform block includes: determining the attribute information of the current transform block based on the residual value and the predicted value of the attribute information of the current transform block.

[0408] In some embodiments, the residual value of the attribute information of the current transform block includes the residual value of the AC coefficient of the current transform block, and the predicted value of the attribute information of the current transform block includes the predicted value of the AC coefficient of the current transform block; determining the attribute information of the current transform block based on the residual value and the predicted value of the attribute information of the current transform block includes: dequantizing the residual value of the AC coefficient of the current transform block, and determining the AC coefficient of the current transform block based on the residual value of the dequantized AC coefficient and the predicted value of the AC coefficient of the current transform block.

[0409] Based on the foregoing embodiments, this application provides a decoding device applied to a point cloud decoder. Figure 18 is a second schematic diagram of the structure of the decoding device provided in this application. As shown in Figure 18, the decoding device 180 includes:

[0410] Decoding module 1801 is configured to decode the bitstream and determine the first syntax element when the current transform layer is a middle or upper layer of the current point cloud.

[0411] The first determining module 1802 is configured to determine the layer prediction mode of the current transform layer according to the first syntax element; wherein the layer prediction mode indicated by the first syntax element is either the second layer prediction mode or the third layer prediction mode; and determine the prediction mode of the current transform block of the current transform layer according to the layer prediction mode of the current transform layer.

[0412] The second determining module 1803 is configured to determine the predicted value of the attribute information of the current transform block based on the prediction mode of the current transform block.

[0413] The third determining module 1804 is configured to determine the attribute information of the current transform block based on the predicted value of the attribute information of the current transform block.

[0414] In some embodiments, the first determining module 1802 is further configured to determine the prediction mode of the current transform block of the current transform layer according to the predefined fourth-layer prediction mode of the lowest layer when the current transform layer is the lowest layer of the current point cloud; the fourth-layer prediction mode includes one or more prediction modes.

[0415] Furthermore, in some embodiments, the fourth-layer prediction mode includes an intra-frame prediction mode, in which the intra-frame prediction mode takes precedence.

[0416] For example, in some embodiments, the fourth-layer prediction mode includes an intra-frame prediction mode and a no-prediction mode, with the intra-frame prediction mode having a higher priority than the no-prediction mode.

[0417] In some embodiments, the second-layer prediction mode includes an inter-frame prediction mode, in which the inter-frame prediction mode takes precedence.

[0418] Furthermore, in some embodiments, the second-layer prediction mode further includes one or more of the following prediction modes:

[0419] Intra-frame prediction mode;

[0420] Unpredictable patterns;

[0421] Average forecast pattern.

[0422] For example, in some embodiments, in the second-layer prediction mode, the priority of the prediction modes from high to low is as follows: inter-frame prediction mode, intra-frame prediction mode, and no prediction mode.

[0423] In some embodiments, the third-layer prediction model includes one or more prediction models.

[0424] Furthermore, in some embodiments, the third-layer prediction mode includes one or more of the following prediction modes:

[0425] Inter-frame prediction mode;

[0426] Intra-frame prediction mode;

[0427] Unpredictable patterns;

[0428] Average forecast pattern.

[0429] For example, in some embodiments, the third-layer prediction modes include inter-frame prediction mode, intra-frame prediction mode, and no prediction mode.

[0430] In some embodiments, determining the prediction mode of the current transform block of the current transform layer includes: if the layer prediction mode indicated by the first syntax element is the third layer prediction mode, decoding the bitstream and determining the second syntax element; and determining the prediction mode of the current transform block based on the value of the second syntax element.

[0431] In some embodiments, the decoding module 1801 is further configured to decode the bitstream and determine a third syntax element; wherein the third syntax element is used to indicate the position of the current transform layer in the middle layer; wherein the value of the third syntax element is equal to a first value, indicating that the current transform layer is in the upper-middle layer of the middle layer.

[0432] In some embodiments, the decoding module 1801 is further configured to decode the bitstream and determine the seventh syntax element when the current transform layer is the upper layer of the current point cloud; the first determining module 1802 is further configured to determine the layer prediction mode of the current transform layer according to the seventh syntax element; and determine the prediction mode of the current transform block of the current transform layer according to the layer prediction mode of the current transform layer; wherein, when the current transform layer is the upper layer, the layer prediction mode indicated by the seventh syntax element is either the tenth layer prediction mode or the eleventh layer prediction mode.

[0433] In some embodiments, the decoding module 1801 is further configured to decode the bitstream and determine the sixth syntax element when the current transform layer is the lowest layer of the current point cloud; the first determining module 1802 is further configured to determine the layer prediction mode of the current transform layer according to the sixth syntax element; and determine the prediction mode of the current transform block of the current transform layer according to the layer prediction mode of the current transform layer; wherein, when the current transform layer is the lowest layer of the current point cloud, the layer prediction mode indicated by the sixth syntax element is either the eighth layer prediction mode or the ninth layer prediction mode.

[0434] In some embodiments, the decoding module 1801 is further configured to decode the bitstream and determine the residual value of the attribute information of the current transform block of the current transform layer.

[0435] In some embodiments, determining the attribute information of the current transform block based on the predicted value of the attribute information of the current transform block includes: determining the attribute information of the current transform block based on the residual value and the predicted value of the attribute information of the current transform block.

[0436] In some embodiments, the residual value of the attribute information of the current transform block includes the residual value of the AC coefficient of the current transform block, and the predicted value of the attribute information of the current transform block includes the predicted value of the AC coefficient of the current transform block; determining the attribute information of the current transform block based on the residual value and the predicted value of the attribute information of the current transform block includes: dequantizing the residual value of the AC coefficient of the current transform block, and determining the AC coefficient of the current transform block based on the residual value of the dequantized AC coefficient and the predicted value of the AC coefficient of the current transform block.

[0437] Based on the foregoing embodiments, this application provides a decoding device applied to a point cloud decoder. Figure 19 is a schematic diagram of the structure of the decoding device provided in this application. As shown in Figure 19, the decoding device 190 includes:

[0438] The first determining module 1901 is configured to determine the prediction mode of the current transform block of the current transform layer based on the predefined fourth-layer prediction mode of the lowest layer when the current transform layer is the lowest layer of the current point cloud; the fourth-layer prediction mode includes one or more prediction modes.

[0439] The second determining module 1902 is configured to determine the predicted value of the attribute information of the current transform block based on the prediction mode of the current transform block.

[0440] The third determining module 1903 is configured to determine the attribute information of the current transform block based on the predicted value of the attribute information of the current transform block.

[0441] In some embodiments, the fourth-layer prediction mode includes an intra-frame prediction mode, in which the intra-frame prediction mode takes precedence.

[0442] For example, in some embodiments, the fourth-layer prediction mode includes an intra-frame prediction mode and a no-prediction mode, with the intra-frame prediction mode having a higher priority than the no-prediction mode.

[0443] In some embodiments, the decoding device 190 further includes a decoding module configured to decode the bitstream and determine a fifth syntax element when the current transform layer is a middle or upper layer of the current point cloud; the first determining module 1901 is further configured to determine the layer prediction mode of the current transform layer based on the fifth syntax element; wherein, when the current transform layer is a middle or upper layer, the layer prediction mode indicated by the fifth syntax element is any one of the fifth layer prediction mode, the sixth layer prediction mode, and the seventh layer prediction mode; and the prediction mode of the current transform block of the current transform layer is determined based on the layer prediction mode of the current transform layer.

[0444] In some embodiments, the decoding device 190 further includes a decoding module configured to decode the bitstream and determine a seventh syntax element when the current transform layer is above the current point cloud; the first determining module 1901 is further configured to determine the layer prediction mode of the current transform layer based on the seventh syntax element; wherein, when the current transform layer is above the current layer, the layer prediction mode indicated by the seventh syntax element is either the tenth layer prediction mode or the eleventh layer prediction mode; and the prediction mode of the current transform block of the current transform layer is determined based on the layer prediction mode of the current transform layer.

[0445] In some embodiments, the decoding device 190 further includes a decoding module configured to decode the bitstream and determine the residual value of the attribute information of the current transform block of the current transform layer.

[0446] In some embodiments, determining the attribute information of the current transform block based on the predicted value of the attribute information of the current transform block includes: determining the attribute information of the current transform block based on the residual value and the predicted value of the attribute information of the current transform block.

[0447] In some embodiments, the residual value of the attribute information of the current transform block includes the residual value of the AC coefficient of the current transform block, and the predicted value of the attribute information of the current transform block includes the predicted value of the AC coefficient of the current transform block; determining the attribute information of the current transform block based on the residual value and the predicted value of the attribute information of the current transform block includes: dequantizing the residual value of the AC coefficient of the current transform block, and determining the AC coefficient of the current transform block based on the residual value of the dequantized AC coefficient and the predicted value of the AC coefficient of the current transform block.

[0448] This application provides an encoding device applied to a point cloud encoder. Figure 20 is a schematic diagram of the structure of the encoding device provided in this application. As shown in Figure 20, the encoding device 200 includes:

[0449] The fourth determining module 2001 is configured to determine the prediction mode of the current transform block of the current transform layer based on the predefined first-layer prediction mode of the upper layer when the current transform layer is the upper layer of the current point cloud; the first-layer prediction mode includes one or more prediction modes.

[0450] The fifth determining module 2002 is configured to determine the predicted value of the attribute information of the current transform block based on the prediction mode of the current transform block;

[0451] The encoding module 2003 is configured to obtain the encoded bits based on the predicted values ​​of the attribute information of the current transform block, and write the encoded bits into the bit stream.

[0452] In some embodiments, the fourth determining module 2001 is further configured to, when the current transform layer is a middle or upper layer of the current point cloud, determine the layer prediction mode of the current transform layer based on the second layer prediction mode and the third layer prediction mode; and determine the prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer.

[0453] In some embodiments, the encoding module 2003 is further configured to, when the current transform layer is a middle or upper layer of the current point cloud, determine the value of the first syntax element according to the layer prediction mode of the current transform layer; encode the value of the first syntax element and write the obtained encoded bits into the bit stream.

[0454] In some embodiments, the fourth determining module 2001 is further configured to determine the prediction mode of the current transform block of the current transform layer according to the predefined fourth layer prediction mode of the lowest layer when the current transform layer is the lowest layer of the current point cloud; the fourth layer prediction mode includes one or more prediction modes.

[0455] In some embodiments, the fourth-layer prediction mode includes an intra-frame prediction mode, in which the intra-frame prediction mode takes precedence.

[0456] For example, in some embodiments, the fourth-layer prediction mode includes an intra-frame prediction mode and a no-prediction mode, with the intra-frame prediction mode having a higher priority than the no-prediction mode.

[0457] In some embodiments, the first-layer prediction mode includes an inter-frame prediction mode, and / or, the second-layer prediction mode includes an inter-frame prediction mode; in the first-layer prediction mode, and / or, in the second-layer prediction mode, the inter-frame prediction mode takes precedence.

[0458] Furthermore, in some embodiments, the first-layer prediction mode further includes one or more of the following prediction modes, and / or the second-layer prediction mode further includes one or more of the following prediction modes:

[0459] Intra-frame prediction mode;

[0460] Unpredictable patterns;

[0461] Average forecast pattern.

[0462] For example, in some embodiments, in the first-layer prediction mode and / or in the second-layer prediction mode, the prediction modes are prioritized from high to low as follows: inter-frame prediction mode, intra-frame prediction mode, and no prediction mode.

[0463] In some embodiments, the third-layer prediction model includes one or more prediction models.

[0464] Furthermore, in some embodiments, the third-layer prediction mode includes one or more of the following prediction modes:

[0465] Inter-frame prediction mode;

[0466] Intra-frame prediction mode;

[0467] Unpredictable patterns;

[0468] Average forecast pattern.

[0469] For example, in some embodiments, the third-layer prediction modes include inter-frame prediction mode, intra-frame prediction mode, and no prediction mode.

[0470] In some embodiments, the encoding module 2003 is further configured to: determine the value of the second syntax element when the layer prediction mode of the current transform layer is the third layer prediction mode; encode the value of the second syntax element and write the obtained encoded bits into the bit stream; wherein the value of the second syntax element is used to indicate the prediction mode of the current transform block of the current transform layer.

[0471] In some embodiments, the encoding module 2003 is further configured to: determine the value of the third syntax element; encode the value of the third syntax element and write the obtained encoded bits into the bit stream; wherein the value of the third syntax element is equal to the first numerical value, indicating that the current transform layer is in the upper-middle layer of the middle layer.

[0472] In some embodiments, the fourth determining module 2001 is further configured to, when the current transform layer is a middle or upper layer of the current point cloud, determine the layer prediction mode of the current transform layer based on the fifth layer prediction mode, the sixth layer prediction mode, and the seventh layer prediction mode; and determine the prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer.

[0473] In some embodiments, the encoding module 2003 is further configured to: determine the value of the fifth syntax element according to the layer prediction mode of the current transformation layer when the current transformation layer is the middle or upper layer of the current point cloud; encode the value of the fifth syntax element and write the obtained encoded bits into the bit stream.

[0474] In some embodiments, the fourth determining module 2001 is further configured to, when the current transform layer is the lowest layer of the current point cloud, determine the layer prediction mode of the current transform layer based on the eighth layer prediction mode and the ninth layer prediction mode; and determine the prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer.

[0475] In some embodiments, the encoding module 2003 is further configured to: determine the value of the sixth syntax element according to the layer prediction mode of the current transformation layer when the current transformation layer is the lowest layer of the current point cloud; encode the value of the sixth syntax element and write the obtained encoded bits into the bit stream.

[0476] In some embodiments, obtaining coded bits based on the predicted values ​​of the attribute information of the current transform block and writing the coded bits into the bitstream includes: determining the residual value of the attribute information of the current transform block based on the predicted values ​​of the attribute information of the current transform block and the attribute information of the current transform block; encoding the residual value of the attribute information of the current transform block; and writing the obtained coded bits into the bitstream.

[0477] In some embodiments, the residual value of the attribute information of the current transform block includes the residual value of the AC coefficients of the current transform block, and the predicted value of the attribute information of the current transform block includes the predicted value of the AC coefficients of the current transform block; encoding the residual value of the attribute information of the current transform block and writing the obtained encoded bits into the bitstream includes: quantizing the residual value of the AC coefficients of the current transform block, encoding the residual value of the quantized AC coefficients, and writing the obtained encoded bits into the bitstream.

[0478] This application provides an encoding device applied to a point cloud encoder. Figure 21 is a second structural schematic diagram of the encoding device provided in this application embodiment. As shown in Figure 21, the encoding device 210 includes:

[0479] The fourth determining module 2101 is configured to, when the current transformation layer is the middle or upper layer of the current point cloud, determine the layer prediction mode of the current transformation layer based on the second layer prediction mode and the third layer prediction mode; and determine the prediction mode of the current transformation block of the current transformation layer based on the layer prediction mode of the current transformation layer.

[0480] The fifth determining module 2102 is configured to determine the predicted value of the attribute information of the current transform block based on the prediction mode of the current transform block;

[0481] The encoding module 2103 is configured to obtain the encoded bits based on the predicted values ​​of the attribute information of the current transform block and write the encoded bits into the bit stream.

[0482] In some embodiments, the encoding module 2103 is further configured to, when the current transform layer is a middle or upper layer of the current point cloud, determine the value of the first syntax element according to the layer prediction mode of the current transform layer; encode the value of the first syntax element and write the obtained encoded bits into the bit stream.

[0483] In some embodiments, the fourth determining module 2101 is further configured to determine the prediction mode of the current transform block of the current transform layer according to the predefined fourth layer prediction mode of the lowest layer when the current transform layer is the lowest layer of the current point cloud; the fourth layer prediction mode includes one or more prediction modes.

[0484] In some embodiments, the fourth-layer prediction mode includes an intra-frame prediction mode, in which the intra-frame prediction mode takes precedence.

[0485] For example, in some embodiments, the fourth-layer prediction mode includes an intra-frame prediction mode and a no-prediction mode, with the intra-frame prediction mode having a higher priority than the no-prediction mode.

[0486] In some embodiments, the second-layer prediction mode includes an inter-frame prediction mode, in which the inter-frame prediction mode takes precedence.

[0487] Furthermore, in some embodiments, the second-layer prediction mode further includes one or more of the following prediction modes:

[0488] Intra-frame prediction mode;

[0489] Unpredictable patterns;

[0490] Average forecast pattern.

[0491] For example, in some embodiments, in the second-layer prediction mode, the priority of the prediction modes from high to low is as follows: inter-frame prediction mode, intra-frame prediction mode, and no prediction mode.

[0492] In some embodiments, the third-layer prediction model includes one or more prediction models.

[0493] Furthermore, in some embodiments, the third-layer prediction mode includes one or more of the following prediction modes:

[0494] Inter-frame prediction mode;

[0495] Intra-frame prediction mode;

[0496] Unpredictable patterns;

[0497] Average forecast pattern.

[0498] In some embodiments, the third-layer prediction modes include: inter-frame prediction mode, intra-frame prediction mode, and no prediction mode.

[0499] In some embodiments, the encoding module 2103 is further configured to: determine the value of the second syntax element when the layer prediction mode of the current transform layer is the third layer prediction mode; encode the value of the second syntax element and write the obtained encoded bits into the bit stream; wherein the value of the second syntax element is used to indicate the prediction mode of the current transform block of the current transform layer.

[0500] In some embodiments, the encoding module 2103 is further configured to: determine the value of the third syntax element; and encode the value of the third syntax element and write the obtained encoded bits into the bit stream; wherein the value of the third syntax element is equal to the first value, indicating that the current transform layer is in the upper-middle layer of the middle layer.

[0501] In some embodiments, the fourth determining module 2101 is further configured to, when the current transform layer is above the current point cloud, determine the layer prediction mode of the current transform layer based on the prediction mode of the tenth layer and the prediction mode of the eleventh layer; and determine the prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer.

[0502] In some embodiments, the encoding module 2103 is further configured to, when the current transform layer is above the current point cloud, determine the value of the seventh syntax element according to the layer prediction mode of the current transform layer; encode the value of the seventh syntax element and write the obtained encoded bits into the bitstream.

[0503] In some embodiments, the fourth determining module 2101 is further configured to, when the current transform layer is the lowest layer of the current point cloud, determine the layer prediction mode of the current transform layer based on the eighth layer prediction mode and the ninth layer prediction mode; and determine the prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer.

[0504] In some embodiments, the encoding module 2103 is further configured to determine the value of the sixth syntax element according to the layer prediction mode of the current transformation layer when the current transformation layer is the lowest layer of the current point cloud; encode the value of the sixth syntax element and write the obtained encoded bits into the bit stream.

[0505] In some embodiments, obtaining coded bits based on the predicted values ​​of the attribute information of the current transform block and writing the coded bits into the bitstream includes: determining the residual value of the attribute information of the current transform block based on the predicted values ​​of the attribute information of the current transform block and the attribute information of the current transform block; encoding the residual value of the attribute information of the current transform block; and writing the obtained coded bits into the bitstream.

[0506] In some embodiments, the residual value of the attribute information of the current transform block includes the residual value of the AC coefficients of the current transform block, and the predicted value of the attribute information of the current transform block includes the predicted value of the AC coefficients of the current transform block; encoding the residual value of the attribute information of the current transform block and writing the obtained encoded bits into the bitstream includes: quantizing the residual value of the AC coefficients of the current transform block, encoding the residual value of the quantized AC coefficients, and writing the obtained encoded bits into the bitstream.

[0507] This application provides an encoding device applied to a point cloud encoder. Figure 22 is a schematic diagram of the structure of the encoding device provided in this application embodiment. As shown in Figure 22, the encoding device 220 includes:

[0508] The fourth determining module 2201 is configured to determine the prediction mode of the current transform block of the current transform layer based on the predefined fourth-layer prediction mode of the lowest layer when the current transform layer is the lowest layer of the current point cloud; the fourth-layer prediction mode includes one or more prediction modes.

[0509] The fifth determining module 2202 is configured to determine the predicted value of the attribute information of the current transform block based on the prediction mode of the current transform block;

[0510] The encoding module 2203 is configured to obtain the encoded bits based on the predicted values ​​of the attribute information of the current transform block and write the encoded bits into the bit stream.

[0511] In some embodiments, the fourth-layer prediction mode includes an intra-frame prediction mode, in which the intra-frame prediction mode takes precedence.

[0512] For example, in some embodiments, the fourth-layer prediction mode includes an intra-frame prediction mode and a no-prediction mode, with the intra-frame prediction mode having a higher priority than the no-prediction mode.

[0513] In some embodiments, the fourth determining module 2201 is further configured to, when the current transform layer is a middle or upper layer of the current point cloud, determine the layer prediction mode of the current transform layer based on the fifth layer prediction mode, the sixth layer prediction mode, and the seventh layer prediction mode; and determine the prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer.

[0514] In some embodiments, the encoding module 2203 is further configured to, when the current transform layer is a middle or upper layer of the current point cloud, determine the value of the fifth syntax element according to the layer prediction mode of the current transform layer; encode the value of the fifth syntax element and write the obtained encoded bits into the bit stream.

[0515] In some embodiments, the fourth determining module 2201 is further configured to, when the current transform layer is above the current point cloud, determine the layer prediction mode of the current transform layer based on the prediction mode of the tenth layer and the prediction mode of the eleventh layer; and determine the prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer.

[0516] In some embodiments, the encoding module 2203 is further configured to, when the current transform layer is above the current point cloud, determine the value of the seventh syntax element according to the layer prediction mode of the current transform layer; encode the value of the seventh syntax element and write the obtained encoded bits into the bit stream.

[0517] In some embodiments, obtaining coded bits based on the predicted values ​​of the attribute information of the current transform block and writing the coded bits into the bitstream includes: determining the residual value of the attribute information of the current transform block based on the predicted values ​​of the attribute information of the current transform block and the attribute information of the current transform block; encoding the residual value of the attribute information of the current transform block; and writing the obtained coded bits into the bitstream.

[0518] In some embodiments, the residual value of the attribute information of the current transform block includes the residual value of the AC coefficients of the current transform block, and the predicted value of the attribute information of the current transform block includes the predicted value of the AC coefficients of the current transform block; encoding the residual value of the attribute information of the current transform block and writing the obtained encoded bits into the bitstream includes: quantizing the residual value of the AC coefficients of the current transform block, encoding the residual value of the quantized AC coefficients, and writing the obtained encoded bits into the bitstream.

[0519] The descriptions of the above device embodiments are similar to those of the above method embodiments, and have similar beneficial effects. For technical details not disclosed in the device embodiments of this application, please refer to the descriptions of the method embodiments of this application for understanding.

[0520] It should be noted that the module division of the apparatus described in the embodiments of this application is illustrative and only represents one logical functional division. In actual implementation, other division methods may be used. Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, exist as separate physical units, or have two or more units integrated into one unit. The integrated units can be implemented in hardware, as software functional units, or a combination of software and hardware.

[0521] It should be noted that, in the embodiments of this application, if the above-described methods are implemented as software functional modules and sold or used as independent products, they can also be stored in a computer-readable storage medium. Based on this understanding, the technical solutions of the embodiments of this application, or the parts that contribute to related technologies, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause an electronic device to execute all or part of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), magnetic disks, or optical disks. Thus, the embodiments of this application are not limited to any specific hardware and software combination.

[0522] This application provides a point cloud decoder, as shown in FIG23. The point cloud decoder 230 includes: a first communication interface 2301, a first memory 2302, and a first processor 2303; the various components are coupled together through a first bus system 2304. It is understood that the first bus system 2304 is used to realize the connection and communication between these components. In addition to a data bus, the first bus system 2304 also includes a power bus, a control bus, and a status signal bus. However, for clarity, all buses are labeled as the first bus system 2304 in FIG23.

[0523] The first communication interface 2301 is used for receiving and sending signals during the process of sending and receiving information with other external network elements;

[0524] The first memory 2302 is used to store computer programs that can run on the first processor 2303;

[0525] The first processor 2303 is configured to execute the decoding method described in the embodiments of this application when running the computer program.

[0526] It is understood that the first memory 2302 in the embodiments of this application can be volatile memory or non-volatile memory, or may include both volatile and non-volatile memory. The non-volatile memory can be read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or flash memory. The volatile memory can be random access memory (RAM), which is used as an external cache. By way of example, but not limitation, many forms of RAM are available, such as Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), Synchronous DRAM (SDRAM), Double Data Rate SDRAM (DDRSDRAM), Enhanced Synchronous DRAM (ESDRAM), Synchlink DRAM (SLDRAM), and Direct Rambus RAM (DRRAM). The first memory 2302 of the system and method described in this application is intended to include, but is not limited to, these and any other suitable types of memory.

[0527] The first processor 2303 may be an integrated circuit chip with signal processing capabilities. In implementation, each step of the above method can be completed by the integrated logic circuitry in the hardware of the first processor 2303 or by instructions in software form. The first processor 2303 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. It can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this application. The general-purpose processor may be a microprocessor or any conventional processor. The steps of the methods disclosed in the embodiments of this application can be directly embodied in the execution of a hardware decoding processor, or executed by a combination of hardware and software modules in the decoding processor. The software modules may reside in random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, or other mature storage media in the art. The storage medium is located in the first memory 2302. The first processor 2303 reads the information in the first memory 2302 and completes the steps of the above method in conjunction with its hardware.

[0528] It is understood that the embodiments described in this application can be implemented using hardware, software, firmware, middleware, microcode, or a combination thereof. For hardware implementation, the processing unit can be implemented in one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), general-purpose processors, controllers, microcontrollers, microprocessors, other electronic units for performing the functions described in this application, or combinations thereof. For software implementation, the technology described in this application can be implemented through modules (e.g., procedures, functions, etc.) that perform the functions described in this application. Software code can be stored in memory and executed by a processor. The memory can be implemented in the processor or external to the processor.

[0529] Alternatively, as another embodiment, the first processor 2303 is also configured to execute any of the aforementioned decoding method embodiments when running the computer program.

[0530] This application provides a point cloud encoder, as shown in Figure 24. The point cloud encoder 240 includes: a second communication interface 2401, a second memory 2402, and a second processor 2403; the various components are coupled together through a second bus system 2404. It is understood that the second bus system 2404 is used to realize the connection and communication between these components. In addition to a data bus, the second bus system 2404 also includes a power bus, a control bus, and a status signal bus. However, for clarity, all buses are labeled as the second bus system 2404 in Figure 24.

[0531] The second communication interface 2401 is used for receiving and sending signals during the process of sending and receiving information with other external network elements;

[0532] The second memory 2402 is used to store computer programs that can run on the second processor 2403;

[0533] The second processor 2403 is used to execute the encoding method described in the embodiments of this application when running the computer program.

[0534] Alternatively, as another embodiment, the second processor 2403 is also configured to execute the aforementioned encoding method embodiment when running the computer program.

[0535] It is understood that the second memory 2402 has similar hardware functions to the first memory 2302, and the second processor 2403 has similar hardware functions to the first processor 2303; details will not be elaborated here.

[0536] This application provides an electronic device, including: a processor adapted to execute a computer program; and a computer-readable storage medium storing the computer program, which, when executed by the processor, implements the encoding and / or decoding methods described in this application. The electronic device can be various types of devices with point cloud encoding and / or point cloud decoding capabilities, such as mobile phones, tablets, laptops, personal computers, televisions, projection devices, or monitoring devices.

[0537] This application provides a bitstream generated using the encoding method provided in this application.

[0538] This application provides a computer-readable storage medium storing a computer program. When the computer program is executed, it implements the encoding method or the decoding method provided in this application.

[0539] This application provides a computer program product, including computer program instructions that cause a computer to perform an encoding method as provided in this application embodiment, or that cause a computer to perform a decoding method as provided in this application embodiment.

[0540] It should be noted that the descriptions of the point cloud codec, electronic device, storage medium, and computer program product embodiments above are similar to the descriptions of the method embodiments above, and have similar beneficial effects. For technical details not disclosed in the point cloud codec, electronic device, storage medium, and computer program product embodiments of this application, please refer to the descriptions of the method embodiments of this application for understanding.

[0541] It should be understood that the phrases "one embodiment," "an embodiment," or "some embodiments" mentioned throughout the specification mean that a specific feature, structure, or characteristic related to an embodiment is included in at least one embodiment of this application. Therefore, "in one embodiment," "in one embodiment," or "in some embodiments" appearing throughout the specification do not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. It should be understood that in the various embodiments of this application, the sequence numbers of the above-described processes do not imply a sequential order of execution; the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application. The sequence numbers of the above-described embodiments are merely for descriptive purposes and do not represent the superiority or inferiority of the embodiments. The descriptions of the various embodiments above tend to emphasize the differences between the various embodiments; their similarities or commonalities can be referred to mutually, and for the sake of brevity, they will not be repeated here.

[0542] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three kinds of relationships. For example, object A and / or object B can represent three situations: object A exists alone, object A and object B exist simultaneously, and object B exists alone.

[0543] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0544] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. The embodiments described above are merely illustrative. For example, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods, such as: multiple modules or components can be combined, or integrated into another system, or some features can be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the various components shown or discussed can be through some interfaces, and the indirect coupling or communication connection between devices or modules can be electrical, mechanical, or other forms.

[0545] The modules described above as separate components may or may not be physically separate. The components shown as modules may or may not be physical modules. They may be located in one place or distributed across multiple network units. Some or all of the modules may be selected to achieve the purpose of this embodiment according to actual needs.

[0546] In addition, each functional module in the various embodiments of this application can be integrated into one processing unit, or each module can be a separate unit, or two or more modules can be integrated into one unit; the integrated modules can be implemented in hardware or in the form of hardware plus software functional units.

[0547] Those skilled in the art will understand that all or part of the steps of the above method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it performs the steps of the above method embodiments. The aforementioned storage medium includes various media that can store program code, such as mobile storage devices, read-only memory (ROM), magnetic disks, or optical disks.

[0548] Alternatively, if the integrated units described above are implemented as software functional modules and sold or used as independent products, they can also be stored in a computer-readable storage medium. Based on this understanding, the technical solutions of the embodiments of this application, or the parts that contribute to related technologies, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause an electronic device to execute all or part of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as mobile storage devices, ROMs, magnetic disks, or optical disks.

[0549] The methods disclosed in the several method embodiments provided in this application can be arbitrarily combined to obtain new method embodiments without conflict. The features disclosed in the several product embodiments provided in this application can be arbitrarily combined to obtain new product embodiments without conflict. The features disclosed in the several method or device embodiments provided in this application can be arbitrarily combined to obtain new method embodiments or device embodiments without conflict.

[0550] The above description is merely an embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A decoding method, the method being applied to a point cloud decoder, the method comprising: When the current transformation layer is the upper layer of the current point cloud, the prediction mode of the current transformation block of the current transformation layer is determined according to the predefined first-layer prediction mode of the upper layer; the first-layer prediction mode includes one or more prediction modes. Based on the prediction mode of the current transform block, determine the predicted value of the attribute information of the current transform block; The attribute information of the current transform block is determined based on the predicted value of the attribute information of the current transform block.

2. The method according to claim 1, wherein, The method further includes: If the current transform layer is a middle or upper layer of the current point cloud, decode the bitstream and determine the first syntax element; Based on the first syntax element, determine the layer prediction mode of the current transform layer; Based on the layer prediction mode of the current transform layer, determine the prediction mode of the current transform block of the current transform layer.

3. The method according to claim 2, wherein, When the current transform layer is a middle or upper layer of the current point cloud, the layer prediction mode indicated by the first syntax element is either the second layer prediction mode or the third layer prediction mode.

4. The method according to any one of claims 1 to 3, wherein, The method further includes: When the current transformation layer is the lowest layer of the current point cloud, the prediction mode of the current transformation block of the current transformation layer is determined according to the predefined fourth-layer prediction mode of the lowest layer; the fourth-layer prediction mode includes one or more prediction modes.

5. The method according to claim 4, wherein, The fourth-layer prediction mode includes an intra-frame prediction mode, which takes precedence in the fourth-layer prediction mode.

6. The method according to claim 5, wherein, The fourth-layer prediction mode includes an intra-frame prediction mode and a no-prediction mode, with the intra-frame prediction mode having a higher priority than the no-prediction mode.

7. The method according to any one of claims 1 to 6, wherein, The first-layer prediction mode includes an inter-frame prediction mode, which takes precedence in the first-layer prediction mode.

8. The method according to claim 7, wherein, The first-layer prediction model also includes one or more of the following prediction models: Intra-frame prediction mode; Unpredictable patterns; Average forecast pattern.

9. The method according to claim 8, wherein, In the first layer of prediction modes, the priority of prediction modes from high to low is as follows: inter-frame prediction mode, intra-frame prediction mode, and no prediction mode.

10. The method according to any one of claims 3 to 6, wherein, The second-layer prediction mode includes an inter-frame prediction mode; among the second-layer prediction modes, the inter-frame prediction mode takes precedence.

11. The method according to claim 10, wherein, The second-layer prediction model also includes one or more of the following prediction models: Intra-frame prediction mode; Unpredictable patterns; Average forecast pattern.

12. The method according to claim 11, wherein, In the second-layer prediction mode, the prediction modes are prioritized from high to low as follows: inter-frame prediction mode, intra-frame prediction mode, and no prediction mode.

13. The method according to any one of claims 3 to 6, 10 to 12, wherein, The third-layer prediction model includes one or more prediction models.

14. The method according to claim 13, wherein, The third-layer prediction model includes one or more of the following prediction models: Inter-frame prediction mode; Intra-frame prediction mode; Unpredictable patterns; Average forecast pattern.

15. The method according to any one of claims 13, wherein, Determining the prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer includes: If the layer prediction mode indicated by the first syntax element is the third layer prediction mode, decode the bitstream and determine the second syntax element; The prediction mode of the current transform block is determined based on the value of the second syntax element.

16. The method according to any one of claims 2 to 15, wherein, The method further includes: Decode the bitstream and determine the third syntax element; wherein the third syntax element is used to indicate the position of the current transform layer in the middle layer; wherein the value of the third syntax element is equal to a first value, indicating that the current transform layer is in the upper-middle layer of the middle layer.

17. The method according to claim 1, wherein, The method further includes: If the current transform layer is a middle or upper layer of the current point cloud, decode the bitstream and determine the fifth syntax element; Based on the fifth syntax element, the layer prediction mode of the current transform layer is determined; wherein, when the current transform layer is the upper-middle layer, the layer prediction mode indicated by the fifth syntax element is any one of the fifth layer prediction mode, the sixth layer prediction mode, and the seventh layer prediction mode. Based on the layer prediction mode of the current transform layer, determine the prediction mode of the current transform block of the current transform layer.

18. The method according to claim 1 or 17, wherein, The method further includes: If the current transform layer is the lowest layer of the current point cloud, decode the bitstream and determine the sixth syntax element; Based on the sixth syntax element, the layer prediction mode of the current transform layer is determined; wherein, when the current transform layer is the lowest layer, the layer prediction mode indicated by the sixth syntax element is either the eighth layer prediction mode or the ninth layer prediction mode. Based on the layer prediction mode of the current transform layer, determine the prediction mode of the current transform block of the current transform layer.

19. The method according to any one of claims 1 to 18, wherein, The method further includes: decoding the bitstream to determine the residual value of the attribute information of the current transform block of the current transform layer; Determining the attribute information of the current transform block based on the predicted value of the attribute information of the current transform block includes: The attribute information of the current transform block is determined based on the residual value and the predicted value of the attribute information of the current transform block.

20. The method according to claim 19, wherein, The residual value of the attribute information of the current transform block includes the residual value of the AC coefficient of the current transform block, and the predicted value of the attribute information of the current transform block includes the predicted value of the AC coefficient of the current transform block. The step of determining the attribute information of the current transform block based on the residual value and the predicted value of the attribute information of the current transform block includes: The residual values ​​of the AC coefficients of the current transform block are dequantized, and the AC coefficients of the current transform block are determined based on the residual values ​​of the dequantized AC coefficients and the predicted values ​​of the AC coefficients of the current transform block.

21. A decoding method, the method being applied to a point cloud decoder, the method comprising: If the current transform layer is a middle or upper layer of the current point cloud, decode the bitstream and determine the first syntax element; Based on the first syntax element, the layer prediction mode of the current transform layer is determined; wherein the layer prediction mode indicated by the first syntax element is either the second layer prediction mode or the third layer prediction mode. Based on the layer prediction mode of the current transform layer, determine the prediction mode of the current transform block of the current transform layer; Based on the prediction mode of the current transform block, determine the predicted value of the attribute information of the current transform block; The attribute information of the current transform block is determined based on the predicted value of the attribute information of the current transform block.

22. The method according to claim 21, wherein, The method further includes: When the current transformation layer is the lowest layer of the current point cloud, the prediction mode of the current transformation block of the current transformation layer is determined according to the predefined fourth-layer prediction mode of the lowest layer; the fourth-layer prediction mode includes one or more prediction modes.

23. The method according to claim 22, wherein, The fourth-layer prediction mode includes an intra-frame prediction mode, which takes precedence in the fourth-layer prediction mode.

24. The method according to claim 23, wherein, The fourth-layer prediction mode includes an intra-frame prediction mode and a no-prediction mode, with the intra-frame prediction mode having a higher priority than the no-prediction mode.

25. The method according to any one of claims 21 to 24, wherein, The second-layer prediction mode includes an inter-frame prediction mode, which takes precedence in the second-layer prediction mode.

26. The method of claim 25, wherein, The second-layer prediction model also includes one or more of the following prediction models: Intra-frame prediction mode; Unpredictable patterns; Average forecast pattern.

27. The method according to claim 26, wherein, In the second-layer prediction mode, the prediction modes are prioritized from high to low as follows: inter-frame prediction mode, intra-frame prediction mode, and no prediction mode.

28. The method according to any one of claims 21 to 27, wherein, The third-layer prediction model includes one or more prediction models.

29. The method according to claim 28, wherein, The third-layer prediction model includes one or more of the following prediction models: Inter-frame prediction mode; Intra-frame prediction mode; Unpredictable patterns; Average forecast pattern.

30. The method according to any one of claims 21 to 29, wherein, The layer prediction mode of the current transform layer determines the prediction mode of the current transform block of the current transform layer, including: If the layer prediction mode indicated by the first syntax element is the third layer prediction mode, decode the bitstream and determine the second syntax element; The prediction mode of the current transform block is determined based on the value of the second syntax element.

31. The method according to any one of claims 21 to 29, wherein, The method further includes: Decode the bitstream and determine the third syntax element; wherein the third syntax element is used to indicate the position of the current transform layer in the middle layer; wherein the value of the third syntax element is equal to a first value, indicating that the current transform layer is in the upper-middle layer of the middle layer.

32. The method according to claim 21, wherein, The method further includes: If the current transform layer is above the current point cloud, decode the bitstream and determine the seventh syntax element; The layer prediction mode of the current transform layer is determined based on the seventh syntax element; wherein, when the current transform layer is the upper layer, the layer prediction mode indicated by the seventh syntax element is either the tenth layer prediction mode or the eleventh layer prediction mode.

33. The method according to claim 21 or 32, wherein, The method further includes: If the current transform layer is the lowest layer of the current point cloud, decode the bitstream and determine the sixth syntax element; The layer prediction mode of the current transform layer is determined according to the sixth syntax element; wherein, when the current transform layer is the lowest layer of the current point cloud, the layer prediction mode indicated by the sixth syntax element is either the eighth layer prediction mode or the ninth layer prediction mode.

34. The method according to any one of claims 21 to 33, wherein, The method further includes: decoding the bitstream to determine the residual value of the attribute information of the current transform block of the current transform layer; Determining the attribute information of the current transform block based on the predicted value of the attribute information of the current transform block includes: The attribute information of the current transform block is determined based on the residual value and the predicted value of the attribute information of the current transform block.

35. The method according to claim 34, wherein, The residual value of the attribute information of the current transform block includes the residual value of the AC coefficient of the current transform block, and the predicted value of the attribute information of the current transform block includes the predicted value of the AC coefficient of the current transform block. The step of determining the attribute information of the current transform block based on the residual value and the predicted value of the attribute information of the current transform block includes: The residual values ​​of the AC coefficients of the current transform block are dequantized, and the AC coefficients of the current transform block are determined based on the residual values ​​of the dequantized AC coefficients and the predicted values ​​of the AC coefficients of the current transform block.

36. A decoding method, the method being applied to a point cloud decoder, the method comprising: When the current transformation layer is the lowest layer of the current point cloud, the prediction mode of the current transformation block of the current transformation layer is determined according to the predefined fourth-layer prediction mode of the lowest layer; the fourth-layer prediction mode includes one or more prediction modes. Based on the prediction mode of the current transform block, determine the predicted value of the attribute information of the current transform block; The attribute information of the current transform block is determined based on the predicted value of the attribute information of the current transform block.

37. The method of claim 36, wherein, The fourth-layer prediction mode includes an intra-frame prediction mode, which takes precedence in the fourth-layer prediction mode.

38. The method according to claim 37, wherein, The fourth-layer prediction mode includes an intra-frame prediction mode and a no-prediction mode, with the intra-frame prediction mode having a higher priority than the no-prediction mode.

39. The method according to claim 36, wherein, The method further includes: If the current transform layer is a middle or upper layer of the current point cloud, decode the bitstream and determine the fifth syntax element; Based on the fifth syntax element, the layer prediction mode of the current transform layer is determined; wherein, when the current transform layer is the upper-middle layer, the layer prediction mode indicated by the fifth syntax element is any one of the fifth layer prediction mode, the sixth layer prediction mode, and the seventh layer prediction mode. Based on the layer prediction mode of the current transform layer, determine the prediction mode of the current transform block of the current transform layer.

40. The method according to claim 36 or 39, wherein, The method further includes: If the current transform layer is above the current point cloud, decode the bitstream and determine the seventh syntax element; The layer prediction mode of the current transform layer is determined according to the seventh syntax element; wherein, when the current transform layer is the upper layer, the layer prediction mode indicated by the seventh syntax element is either the tenth layer prediction mode or the eleventh layer prediction mode. Based on the layer prediction mode of the current transform layer, determine the prediction mode of the current transform block of the current transform layer.

41. The method according to any one of claims 36 to 40, wherein, The method further includes: decoding the bitstream to determine the residual value of the attribute information of the current transform block of the current transform layer; Determining the attribute information of the current transform block based on the predicted value of the attribute information of the current transform block includes: The attribute information of the current transform block is determined based on the residual value and the predicted value of the attribute information of the current transform block.

42. The method according to claim 41, wherein, The residual value of the attribute information of the current transform block includes the residual value of the AC coefficient of the current transform block, and the predicted value of the attribute information of the current transform block includes the predicted value of the AC coefficient of the current transform block. The step of determining the attribute information of the current transform block based on the residual value and the predicted value of the attribute information of the current transform block includes: The residual values ​​of the AC coefficients of the current transform block are dequantized, and the AC coefficients of the current transform block are determined based on the residual values ​​of the dequantized AC coefficients and the predicted values ​​of the AC coefficients of the current transform block.

43. An encoding method applied to a point cloud encoder, the method comprising: When the current transformation layer is the upper layer of the current point cloud, the prediction mode of the current transformation block of the current transformation layer is determined according to the predefined first-layer prediction mode of the upper layer; the first-layer prediction mode includes one or more prediction modes. Based on the prediction mode of the current transform block, determine the predicted value of the attribute information of the current transform block; Based on the predicted value of the attribute information of the current transform block, the encoded bits are obtained and written into the bitstream.

44. The method according to claim 43, wherein, The method further includes: When the current transformation layer is a middle or upper layer of the current point cloud, the layer prediction mode of the current transformation layer is determined based on the second layer prediction mode and the third layer prediction mode. Based on the layer prediction mode of the current transform layer, determine the prediction mode of the current transform block of the current transform layer.

45. The method according to claim 44, wherein, The method further includes: When the current transformation layer is a middle or upper layer of the current point cloud, the value of the first syntax element is determined according to the layer prediction mode of the current transformation layer. The value of the first syntax element is encoded, and the resulting encoded bits are written into the bitstream.

46. ​​The method according to any one of claims 43 to 45, wherein, The method further includes: When the current transformation layer is the lowest layer of the current point cloud, the prediction mode of the current transformation block of the current transformation layer is determined according to the predefined fourth-layer prediction mode of the lowest layer; the fourth-layer prediction mode includes one or more prediction modes.

47. The method according to claim 46, wherein, The fourth-layer prediction mode includes an intra-frame prediction mode, which takes precedence in the fourth-layer prediction mode.

48. The method according to claim 46, wherein, The fourth-layer prediction mode includes an intra-frame prediction mode and a no-prediction mode, with the intra-frame prediction mode having a higher priority than the no-prediction mode.

49. The method according to any one of claims 43 to 48, wherein, The first-layer prediction mode includes an inter-frame prediction mode, which takes precedence in the first-layer prediction mode.

50. The method according to claim 49, wherein, The first-layer prediction model also includes one or more of the following prediction models: Intra-frame prediction mode; Unpredictable patterns; Average forecast pattern.

51. The method according to claim 50, wherein, In the first layer of prediction modes, the priority of prediction modes from high to low is as follows: inter-frame prediction mode, intra-frame prediction mode, and no prediction mode.

52. The method according to claim 44, wherein, The second-layer prediction mode includes an inter-frame prediction mode; among the second-layer prediction modes, the inter-frame prediction mode takes precedence.

53. The method according to claim 52, wherein, The second-layer prediction model also includes one or more of the following prediction models: Intra-frame prediction mode; Unpredictable patterns; Average forecast pattern.

54. The method according to claim 53, wherein, In the second-level prediction mode, the prediction modes are prioritized from high to low as follows: inter-frame prediction mode, intra-frame prediction mode, and no prediction mode.

55. The method according to any one of claims 44, 52 to 54, wherein, The third-layer prediction model includes one or more prediction models.

56. The method according to claim 55, wherein, The third-layer prediction model includes one or more of the following prediction models: Inter-frame prediction mode; Intra-frame prediction mode; Unpredictable patterns; Average forecast pattern.

57. The method according to claim 44, 55 or 56, wherein, The method further includes: If the layer prediction mode indicated by the first syntax element is the third layer prediction mode, determine the value of the second syntax element. The value of the second syntax element is encoded, and the resulting encoded bits are written into the bitstream; wherein the value of the second syntax element is used to indicate the prediction mode of the current transform block of the current transform layer.

58. The method according to claim 44, wherein, The method further includes: Determine the value of the third syntax element; The value of the third syntax element is encoded, and the resulting encoded bits are written into the bitstream; wherein the value of the third syntax element is equal to the first value, indicating that the current transform layer is the upper-middle layer in the middle layer.

59. The method according to claim 43, wherein, The method further includes: When the current transformation layer is a middle or upper layer of the current point cloud, the layer prediction mode of the current transformation layer is determined according to the fifth layer prediction mode, the sixth layer prediction mode, and the seventh layer prediction mode. Based on the layer prediction mode of the current transform layer, determine the prediction mode of the current transform block of the current transform layer.

60. The method according to claim 59, wherein, The method further includes: When the current transformation layer is a middle or upper layer of the current point cloud, the value of the fifth syntax element is determined according to the layer prediction mode of the current transformation layer. The value of the fifth syntax element is encoded, and the resulting encoded bits are written into the bitstream.

61. The method according to claim 43 or 59, wherein, The method further includes: When the current transformation layer is the lowest layer of the current point cloud, the layer prediction mode of the current transformation layer is determined according to the eighth layer prediction mode and the ninth layer prediction mode. Based on the layer prediction mode of the current transform layer, determine the prediction mode of the current transform block of the current transform layer.

62. The method according to claim 61, wherein, The method further includes: When the current transform layer is the lowest layer of the current point cloud, the value of the sixth syntax element is determined according to the layer prediction mode of the current transform layer. The value of the sixth syntax element is encoded, and the resulting encoded bits are written into the bitstream.

63. The method according to any one of claims 43 to 62, wherein, The step of obtaining the encoded bits based on the predicted values ​​of the attribute information of the current transform block and writing the encoded bits into the bitstream includes: Based on the predicted value of the attribute information of the current transform block and the attribute information of the current transform block, determine the residual value of the attribute information of the current transform block; The residual values ​​of the attribute information of the current transform block are encoded, and the resulting encoded bits are written into the bitstream.

64. The method according to claim 63, wherein, The residual value of the attribute information of the current transform block includes the residual value of the AC coefficient of the current transform block, and the predicted value of the attribute information of the current transform block includes the predicted value of the AC coefficient of the current transform block. Encoding the residual values ​​of the attribute information of the current transform block and writing the resulting encoded bits into the bitstream includes: The residual values ​​of the AC coefficients of the current transform block are quantized, the quantized residual values ​​of the AC coefficients are encoded, and the resulting encoded bits are written into the bitstream.

65. An encoding method applied to a point cloud encoder, the method comprising: When the current transformation layer is a middle or upper layer of the current point cloud, the layer prediction mode of the current transformation layer is determined based on the second layer prediction mode and the third layer prediction mode. Based on the layer prediction mode of the current transform layer, determine the prediction mode of the current transform block of the current transform layer; Based on the prediction mode of the current transform block, determine the predicted value of the attribute information of the current transform block; Based on the predicted value of the attribute information of the current transform block, the encoded bits are obtained and written into the bitstream.

66. The method according to claim 65, wherein, The method further includes: When the current transformation layer is a middle or upper layer of the current point cloud, the value of the first syntax element is determined according to the layer prediction mode of the current transformation layer. The value of the first syntax element is encoded, and the resulting encoded bits are written into the bitstream.

67. The method according to claim 65 or 66, wherein, The method further includes: When the current transformation layer is the lowest layer of the current point cloud, the prediction mode of the current transformation block of the current transformation layer is determined according to the predefined fourth-layer prediction mode of the lowest layer; the fourth-layer prediction mode includes one or more prediction modes.

68. The method according to claim 67, wherein, The fourth-layer prediction mode includes an intra-frame prediction mode, which takes precedence in the fourth-layer prediction mode.

69. The method according to claim 68, wherein, The fourth-layer prediction mode includes an intra-frame prediction mode and a no-prediction mode, with the intra-frame prediction mode having a higher priority than the no-prediction mode.

70. The method according to any one of claims 65 to 69, wherein, The second-layer prediction mode includes an inter-frame prediction mode, which takes precedence in the second-layer prediction mode.

71. The method according to claim 70, wherein, The second-layer prediction model also includes one or more of the following prediction models: Intra-frame prediction mode; Unpredictable patterns; Average forecast pattern.

72. The method according to claim 71, wherein, In the second-layer prediction mode, the prediction modes are prioritized from high to low as follows: inter-frame prediction mode, intra-frame prediction mode, and no prediction mode.

73. The method according to any one of claims 65 to 73, wherein, The third-layer prediction model includes one or more prediction models.

74. The method according to claim 73, wherein, The third-layer prediction model includes one or more of the following prediction models: Inter-frame prediction mode; Intra-frame prediction mode; Unpredictable patterns; Average forecast pattern.

75. The method according to any one of claims 65 to 74, wherein, The method further includes: If the current transformation layer prediction mode is the third layer prediction mode, determine the value of the second syntax element; The value of the second syntax element is encoded, and the resulting encoded bits are written into the bitstream; wherein the value of the second syntax element is used to indicate the prediction mode of the current transform block of the current transform layer.

76. The method according to any one of claims 65 to 74, wherein, The method further includes: Determine the value of the third syntax element; The value of the third syntax element is encoded, and the resulting encoded bits are written into the bitstream; wherein the value of the third syntax element is equal to the first value, indicating that the current transform layer is the upper-middle layer in the middle layer.

77. The method of claim 65, wherein, The method further includes: When the current transformation layer is above the current point cloud, the layer prediction mode of the current transformation layer is determined based on the prediction modes of the tenth and eleventh layers.

78. The method according to claim 77, wherein, The method further includes: When the current transformation layer is above the current point cloud, the layer prediction mode of the current transformation layer is determined. The values ​​that the seventh syntax element can take; The value of the seventh syntax element is encoded, and the resulting encoded bits are written into the bitstream.

79. The method according to claim 65 or 77, wherein, The method further includes: When the current transformation layer is the lowest layer of the current point cloud, the layer prediction mode of the current transformation layer is determined based on the eighth layer prediction mode and the ninth layer prediction mode.

80. The method according to claim 79, wherein, The method further includes: When the current transform layer is the lowest layer of the current point cloud, the value of the sixth syntax element is determined according to the layer prediction mode of the current transform layer. The value of the sixth syntax element is encoded, and the resulting encoded bits are written into the bitstream.

81. The method according to any one of claims 65 to 80, wherein, The step of obtaining the encoded bits based on the predicted values ​​of the attribute information of the current transform block and writing the encoded bits into the bitstream includes: Based on the predicted value of the attribute information of the current transform block and the attribute information of the current transform block, determine the residual value of the attribute information of the current transform block; The residual values ​​of the attribute information of the current transform block are encoded, and the resulting encoded bits are written into the bitstream.

82. The method according to claim 81, wherein, The residual value of the attribute information of the current transform block includes the residual value of the AC coefficient of the current transform block, and the predicted value of the attribute information of the current transform block includes the predicted value of the AC coefficient of the current transform block. Encoding the residual values ​​of the attribute information of the current transform block and writing the resulting encoded bits into the bitstream includes: The residual values ​​of the AC coefficients of the current transform block are quantized, the quantized residual values ​​of the AC coefficients are encoded, and the resulting encoded bits are written into the bitstream.

83. An encoding method applied to a point cloud encoder, the method comprising: When the current transformation layer is the lowest layer of the current point cloud, the prediction mode of the current transformation block of the current transformation layer is determined according to the predefined fourth-layer prediction mode of the lowest layer; the fourth-layer prediction mode includes one or more prediction modes. Based on the prediction mode of the current transform block, determine the predicted value of the attribute information of the current transform block; Based on the predicted value of the attribute information of the current transform block, the encoded bits are obtained and written into the bitstream.

84. The method according to claim 83, wherein, The fourth-layer prediction mode includes an intra-frame prediction mode, which takes precedence in the fourth-layer prediction mode.

85. The method according to claim 84, wherein, The fourth-layer prediction mode includes an intra-frame prediction mode and a no-prediction mode, with the intra-frame prediction mode having a higher priority than the no-prediction mode.

86. The method according to claim 83, wherein, The method further includes: When the current transformation layer is a middle or upper layer of the current point cloud, the layer prediction mode of the current transformation layer is determined according to the fifth layer prediction mode, the sixth layer prediction mode, and the seventh layer prediction mode. Based on the layer prediction mode of the current transform layer, determine the prediction mode of the current transform block of the current transform layer.

87. The method according to claim 86, wherein, The method further includes: When the current transformation layer is a middle or upper layer of the current point cloud, the value of the fifth syntax element is determined according to the layer prediction mode of the current transformation layer. The value of the fifth syntax element is encoded, and the resulting encoded bits are written into the bitstream.

88. The method according to claim 83 or 86, wherein, The method further includes: When the current transformation layer is above the current point cloud, the layer prediction mode of the current transformation layer is determined according to the prediction mode of the tenth layer and the prediction mode of the eleventh layer. Based on the layer prediction mode of the current transform layer, determine the prediction mode of the current transform block of the current transform layer.

89. The method according to claim 88, wherein, The method further includes: When the current transformation layer is above the current point cloud, the value of the seventh syntax element is determined according to the layer prediction mode of the current transformation layer. The value of the seventh syntax element is encoded, and the resulting encoded bits are written into the bitstream.

90. The method according to any one of claims 83 to 89, wherein, Based on the predicted values ​​of the attribute information of the current transform block, the encoded bits are obtained, and the encoded bits are written into the bitstream, including: Based on the predicted value of the attribute information of the current transform block and the attribute information of the current transform block, determine the residual value of the attribute information of the current transform block; The residual values ​​of the attribute information of the current transform block are encoded, and the resulting encoded bits are written into the bitstream.

91. The method according to claim 90, wherein, The residual value of the attribute information of the current transform block includes the residual value of the AC coefficient of the current transform block, and the predicted value of the attribute information of the current transform block includes the predicted value of the AC coefficient of the current transform block. Encoding the residual values ​​of the attribute information of the current transform block and writing the resulting encoded bits into the bitstream includes: The residual values ​​of the AC coefficients of the current transform block are quantized, the quantized residual values ​​of the AC coefficients are encoded, and the resulting encoded bits are written into the bitstream.

92. A decoding apparatus applied to a point cloud decoder, the apparatus comprising: The first determining module is configured to determine the prediction mode of the current transform block of the current transform layer based on the predefined first-layer prediction mode of the upper layer when the current transform layer is the upper layer of the current point cloud; the first-layer prediction mode includes one or more prediction modes. The second determining module is configured to determine the predicted value of the attribute information of the current transform block based on the prediction mode of the current transform block. The third determining module is configured to determine the attribute information of the current transform block based on the predicted value of the attribute information of the current transform block.

93. A decoding apparatus applied to a point cloud decoder, the apparatus comprising: The decoding module is configured to decode the bitstream and determine the first syntax element when the current transform layer is a middle or upper layer of the current point cloud. The first determining module is configured to determine the layer prediction mode of the current transform layer based on the first syntax element; and to determine the prediction mode of the current transform block of the current transform layer based on the layer prediction mode of the current transform layer; wherein the layer prediction mode indicated by the first syntax element is either the second layer prediction mode or the third layer prediction mode. The second determining module is configured to determine the predicted value of the attribute information of the current transform block based on the prediction mode of the current transform block. The third determining module is configured to determine the attribute information of the current transform block based on the predicted value of the attribute information of the current transform block.

94. A decoding apparatus applied to a point cloud decoder, the apparatus comprising: The first determining module is configured to determine the prediction mode of the current transform block of the current transform layer based on the predefined fourth-layer prediction mode of the lowest layer when the current transform layer is the lowest layer of the current point cloud; the fourth-layer prediction mode includes one or more prediction modes. The second determining module is configured to determine the predicted value of the attribute information of the current transform block based on the prediction mode of the current transform block. The third determining module is configured to determine the attribute information of the current transform block based on the predicted value of the attribute information of the current transform block.

95. A point cloud decoder, comprising a first memory and a first processor; wherein, The first memory is used to store computer programs that can run on the first processor; The first processor is configured to, when running the computer program, perform the method as described in any one of claims 1 to 20, or perform the method as described in any one of claims 21 to 35, or perform the method as described in any one of claims 36 to 42.

96. An encoding device applied to a point cloud encoder, the device comprising: The fourth determining module is configured to, when the current transformation layer is the upper layer of the current point cloud, determine the prediction mode of the current transformation block of the current transformation layer according to the predefined first-layer prediction mode of the upper layer; the first-layer prediction mode includes one or more prediction modes. The fifth determining module is configured to determine the predicted value of the attribute information of the current transform block based on the prediction mode of the current transform block; The encoding module is configured to obtain encoded bits based on the predicted values ​​of the attribute information of the current transform block, and write the encoded bits into the bit stream.

97. An encoding device applied to a point cloud encoder, the device comprising: The fourth determining module is configured to determine the layer prediction mode of the current transformation layer based on the second layer prediction mode and the third layer prediction mode when the current transformation layer is the middle or upper layer of the current point cloud. The fourth determining module is configured to determine the current transform block of the current transform layer based on the layer prediction mode of the current transform layer. Predictive patterns; The fifth determining module is configured to determine the predicted value of the attribute information of the current transform block based on the prediction mode of the current transform block; The encoding module is configured to obtain encoded bits based on the predicted values ​​of the attribute information of the current transform block, and write the encoded bits into the bit stream.

98. An encoding device applied to a point cloud encoder, the device comprising: The fourth determining module is configured to, when the current transform layer is the lowest layer of the current point cloud, determine the prediction mode of the current transform block of the current transform layer according to the predefined fourth layer prediction mode of the lowest layer; the fourth layer prediction mode includes one or more prediction modes. The fifth determining module is configured to determine the predicted value of the attribute information of the current transform block based on the prediction mode of the current transform block; The encoding module is configured to obtain encoded bits based on the predicted values ​​of the attribute information of the current transform block, and write the encoded bits into the bit stream.

99. A point cloud encoder, comprising a second memory and a second processor; wherein, The second memory is used to store computer programs that can run on the second processor; The second processor is configured to, when running the computer program, perform the method as described in any one of claims 43 to 64, or perform the method as described in any one of claims 65 to 82, or perform the method as described in any one of claims 83 to 91.

100. A bitstream generated by the encoding method of any one of claims 43 to 64, or by the encoding method of any one of claims 65 to 82, or by the encoding method of any one of claims 83 to 91.

101. An electronic device, comprising: A processor, adapted to execute computer programs; A computer-readable storage medium storing a computer program that, when executed by the processor, implements the decoding method as described in any one of claims 1 to 42, or, when executed by the processor, implements the encoding method as described in any one of claims 43 to 91.

102. A computer-readable storage medium, wherein, The computer-readable storage medium stores a computer program that, when executed, implements the method as claimed in any one of claims 1 to 20, or the method as claimed in any one of claims 21 to 35, or the method as claimed in any one of claims 36 to 42, or the method as claimed in any one of claims 43 to 64, or the method as claimed in any one of claims 65 to 82, or the method as claimed in any one of claims 93 to 91.

103. A computer program product comprising computer program instructions that cause a computer to perform the method as claimed in any one of claims 1 to 20, or the method as claimed in any one of claims 21 to 35, or the method as claimed in any one of claims 36 to 42, or the method as claimed in any one of claims 43 to 64, or the method as claimed in any one of claims 65 to 82, or the method as claimed in any one of claims 83 to 91.

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