Mesh decoding device, mesh encoding device, mesh decoding method and program

Abstract

To improve the efficiency of coding a mesh.SOLUTION: A displacement amount decoding unit 206 of a mesh decoder 200 of the present invention includes: a picture decoding unit 2061 for outputting a picture from a displacement amount bit stream; an image development unit 2062 for developing each image as a level value and outputting the image; an inverse quantization unit 2063 for inverse-quantizing the level value and generating a conversion coefficient; and a reverse-wavelet transforming unit 2064 for generating a displacement amount by performing a reverse-wavelet transform on the conversion coefficient.SELECTED DRAWING: Figure 37

Description

[Technical field]

[0001] The present invention relates to a mesh decoding device, a mesh encoding device, a mesh decoding method, and a program. [Background technology]

[0002] Non-Patent Document 1 discloses a technique for encoding a mesh using Non-Patent Document 2. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Cfp for Dynamic Mesh Coding, ISO / IEC JTC1 / SC29 / WG7 N00231, MPEG136 - Online [Non-Patent Document 2] Google Draco, accessed May 26, 2022 [Online], https: / / google.github.io / draco Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional technology, the coordinates and connection information of all vertices constituting a dynamic mesh are losslessly encoded, so that the amount of information cannot be reduced even under conditions where loss is acceptable, resulting in low encoding efficiency. Therefore, the present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a mesh decoding device, a mesh encoding device, a mesh decoding method, and a program that can improve the encoding efficiency of a mesh. [Means for solving the problem]

[0005] A first feature of the present invention is a mesh decoding device comprising a displacement amount decoding unit configured to decode a displacement amount bit stream to generate and output a displacement amount, wherein the displacement amount decoding unit comprises a video decoding unit configured to output a video by decoding the displacement amount bit stream by video coding, an image expansion unit configured to expand the video as level values ​​for each image and output the expanded video, an inverse quantization unit configured to generate transform coefficients by inverse quantizing the level values, and an inverse wavelet transform unit configured to generate the displacement amount by applying an inverse wavelet transform to the transform coefficients.

[0006] A second feature of the present invention is a mesh decoding method comprising the steps of: outputting an image by decoding a displacement bitstream using a video encoding method; generating level values ​​by expanding the image for each image; generating transform coefficients by inverse quantizing the level values; and generating a displacement by applying an inverse wavelet transform to the transform coefficients.

[0007] A third feature of the present invention is summarized as a program for causing a computer to function as a mesh decoding device, the mesh decoding device comprising a displacement amount decoding unit configured to decode a displacement amount bit stream to generate and output a displacement amount, the displacement amount decoding unit comprising a video decoding unit configured to output a video by decoding the displacement amount bit stream using video coding, a decoding unit configured to output a level value by expanding the video for each image, an inverse quantization unit configured to generate a transform coefficient by inverse quantizing the level value, and an inverse wavelet transform unit configured to generate the displacement amount by applying an inverse wavelet transform to the transform coefficient. Effect of the Invention

[0008] According to the present invention, it is possible to provide a mesh decoding device, a mesh encoding device, a mesh decoding method, and a program capable of improving mesh encoding efficiency. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a mesh processing system 1 according to an embodiment. [Diagram 2] FIG. 2 is a diagram illustrating an example of functional blocks of a mesh decoding device 200 according to an embodiment. [Figure 3A] FIG. 3A is a diagram showing an example of a base mesh and a subdivision mesh. [Figure 3B] FIG. 3B is a diagram showing an example of a base mesh and a subdivision mesh. [Figure 4] FIG. 4 is a diagram showing an example of a syntax configuration of a basic mesh bit stream. [Diagram 5] FIG. 5 is a diagram illustrating an example of a syntax configuration of the BPH. [Figure 6] FIG. 6 is a diagram showing an example of functional blocks of the basic mesh decoding unit 202 of the mesh decoding device 200 according to an embodiment. [Figure 7] FIG. 7 is a diagram showing an example of the correspondence between the vertices of the basic mesh of a P frame and the vertices of the basic mesh of an I frame. [Figure 8] FIG. 8 is a diagram showing an example of functional blocks of an inter decoding unit 202E of the basic mesh decoding unit 202 of the mesh decoding device 200 according to an embodiment. [Figure 9] FIG. 9 is a diagram illustrating an example of a method for calculating the MVP of a vertex to be decoded by the motion vector prediction unit 202E3 of the inter decoding unit 202E of the basic mesh decoding unit 202 of the mesh decoding device 200 according to one embodiment. [Figure 10] FIG. 10 shows a flowchart illustrating an example of the operation of the motion vector prediction unit 202E3 of the inter decoding unit 202E of the basic mesh decoding unit 202 of the mesh decoding device 200 according to one embodiment. [Figure 11] FIG. 11 shows a flowchart illustrating an example of the operation of the motion vector prediction unit 202E3 of the inter decoding unit 202E of the basic mesh decoding unit 202 of the mesh decoding device 200 according to one embodiment, calculating the sum Total_D of distances to surrounding decoded vertices. [Figure 12] FIG. 12 is a flowchart showing an example of operation of the motion vector prediction unit 202E3 of the inter decoding unit 202E of the basic mesh decoding unit 202 of the mesh decoding device 200 according to one embodiment, calculating the MVP using a weighted average. [Figure 13] FIG. 13 is a flowchart showing an example of the operation of the motion vector prediction unit 202E3 of the inter decoding unit 202E of the basic mesh decoding unit 202 of the mesh decoding device 200 according to one embodiment, selecting an MV from a set of candidate MVs as an MVP. [Figure 14] FIG. 14 is a flowchart showing an example of an operation of the motion vector prediction unit 202E3 of the inter decoding unit 202E of the basic mesh decoding unit 202 of the mesh decoding device 200 according to one embodiment, whereby the motion vector prediction unit 202E3 creates a set of candidate MVs. [Figure 15] FIG. 15 is a diagram illustrating an example of parallelogram prediction. [Figure 16] FIG. 16 is a flowchart showing an example of an operation for restoring the MVR precision to the original bit precision from adaptive_mesh_flag, adaptive_bit_flag, and precision control parameters, which are control information generated by decoding a basic mesh bit stream. [Figure 17] FIG. 17 is intended to illustrate an example of MVR encoding. [Figure 18] FIG. 18 is a diagram showing an example of functional blocks of an inter decoding unit 202E of the basic mesh decoding unit 202 of the mesh decoding device 200 according to an embodiment. [Figure 19] FIG. 19 is a diagram showing an example of an operation for determining connection information and the order of vertices using Edgebreaker. [Figure 20]FIG. 20 is a diagram showing an example of functional blocks of the subdivision unit 203 of the mesh decoding device 200 according to an embodiment. [Figure 21] FIG. 21 is a diagram showing an example of functional blocks of the basic mesh subdivision unit 203A of the subdivision unit 203 of the mesh decoding device 200 according to an embodiment. [Figure 22] FIG. 22 is a diagram illustrating an example of a method for dividing a base surface by the basic surface dividing unit 203A5 of the basic mesh subdivision unit 203A of the subdivision unit 203 in the mesh decoding device 200 according to an embodiment. [Figure 23] FIG. 23 is a flowchart showing an example of the operation of the basic mesh subdivision unit 203A of the subdivision unit 203 of the mesh decoding device 200 according to an embodiment. [Figure 24] FIG. 24 is a diagram showing an example of functional blocks of the subdivision mesh adjustment unit 203B of the subdivision unit 203 of the mesh decoding device 200 according to an embodiment. [Diagram 25] FIG. 25 is a diagram showing an example of a case in which an edge division point on a basic surface ABC is moved by the edge division point moving unit 701 of the subdivision mesh adjustment unit 203B of the subdivision unit 203 of the mesh decoding device 200 according to an embodiment. [Figure 26] FIG. 26 is a diagram showing an example of a case in which subdivision surface X in a base surface is re-subdivided by the subdivision surface division unit 702 of the subdivision mesh adjustment unit 203B of the subdivision unit 203 of the mesh decoding device 200 according to one embodiment. [Figure 27] FIG. 27 is a diagram showing an example of a case in which all subdivision surfaces are re-subdivided by the subdivision surface division unit 702 of the subdivision mesh adjustment unit 203B of the subdivision unit 203 of the mesh decoding device 200 according to one embodiment. [Figure 28] FIG. 28 is a diagram showing an example of functional blocks of the displacement amount decoding unit 206 of the mesh decoding device 200 according to one embodiment (when inter prediction is performed in the spatial domain). [Figure 29] FIG. 29 is a diagram showing an example of the configuration of a displacement amount bit stream. [Diagram 30]FIG. 30 is a diagram showing an example of a syntax configuration of a DPS. [Diagram 31] FIG. 31 is a diagram illustrating an example of a syntax configuration of the DPH. [Diagram 32] FIG. 32 is a diagram illustrating an example of a correspondence relationship between subdivision vertices between a reference frame and a current frame for decoding when inter prediction is performed in the spatial domain. [Diagram 33] FIG. 33 is a diagram showing an example of functional blocks of the displacement amount decoding unit 206 of the mesh decoding device 200 according to one embodiment (when inter prediction is performed in the frequency domain). [Diagram 34] FIG. 34 is a diagram illustrating an example of a correspondence relationship in frequency between a reference frame and a current frame to be decoded when inter prediction is performed in the frequency domain. [Diagram 35] FIG. 35 is a flowchart showing an example of the operation of the displacement amount decoding unit 206 of the mesh decoding device 200 according to an embodiment. [Diagram 36] FIG. 36 is a diagram illustrating an example of functional blocks of the displacement amount decoding unit 206 according to the first modification. [Figure 37] FIG. 37 is a diagram illustrating an example of functional blocks of the displacement amount decoding unit 206 according to the second modification. [Figure 38] FIG. 38 is a diagram showing an example of functional blocks of an inter decoding unit 202E of the basic mesh decoding unit 202 of the mesh decoding device 200 according to one embodiment. [Figure 39] FIG. 39 is a diagram showing an example of functional blocks of the intra decoding unit 202B of the basic mesh decoding unit 202 of the mesh decoding device 200 according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments of the present invention will be described with reference to the drawings. Note that the components in the following embodiments can be appropriately replaced with existing components, and various variations including combinations with other existing components are possible. Therefore, the description of the following embodiments does not limit the content of the invention described in the claims.

[0011] First Embodiment The mesh processing system according to this embodiment will be described below with reference to FIGS.

[0012] 1 is a diagram showing an example of the configuration of a mesh processing system 1 according to this embodiment. As shown in FIG.

[0013] FIG. 2 is a diagram showing an example of functional blocks of the mesh decoding device 200 according to this embodiment.

[0014] As shown in FIG. 2, the mesh decoding device 200 includes a demultiplexing unit 201, a basic mesh decoding unit 202, a subdivision unit 203, a mesh decoding unit 204, a patch integration unit 205, a displacement amount decoding unit 206, and a video decoding unit 207.

[0015] Here, the basic mesh decoding unit 202, the subdivision unit 203, the mesh decoding unit 204 and the displacement amount decoding unit 206 are configured to perform processing on a patch basis into which the mesh is divided, and the results of this processing may then be configured to be integrated by the patch integration unit 205.

[0016] In the example of FIG. 3A, the mesh is divided into patch 1 consisting of basic faces 1 and 2, and patch 2 consisting of basic faces 3 and 4.

[0017] The demultiplexing unit 201 is configured to separate the multiplexed bit stream into a base mesh bit stream, a displacement amount bit stream, and a texture bit stream.

[0018] <Basic mesh decoding unit 202> The base mesh decoding unit 202 is configured to decode the base mesh bitstream and generate and output a base mesh.

[0019] Here, the base mesh is composed of a plurality of vertices in a three-dimensional space and edges connecting these vertices.

[0020] As shown in FIG. 3A, the basic mesh is formed by combining basic faces each represented by three vertices.

[0021] The base mesh decoder 202 may be configured to decode the base mesh bitstream using, for example, Draco as described in Non-Patent Document 2.

[0022] Furthermore, the basic mesh decoding unit 202 may be configured to generate "subdivision_method_id" (described later) as control information for controlling the type of subdivision method.

[0023] Hereinafter, the control information decoded by the basic mesh decoding unit 202 will be described with reference to Figs.

[0024] FIG. 4 is a diagram showing an example of a syntax configuration of a basic mesh bit stream.

[0025] As shown in Fig. 4, first, the base mesh bitstream may include a BPH (Base Patch Header), which is a set of control information corresponding to the base mesh patch. Second, the base mesh bitstream may include, following the BPH, base mesh patch data that encodes the base mesh patch.

[0026] As described above, the basic mesh bit stream is configured such that each patch data corresponds to one BPH. Note that the configuration of Fig. 4 is merely an example, and as long as each patch data corresponds to a BPH, elements other than those described above may be added as components of the basic mesh bit stream.

[0027] For example, as shown in FIG. 4, the basic mesh bit stream may include an SPS (Sequence Parameter Set), an FH (Frame Header) which is a collection of control information corresponding to a frame, or an MH (Mesh Header) which is control information corresponding to a mesh.

[0028] 5 is a diagram showing an example of the syntax configuration of the BPH. Here, if the syntax functions are similar, different syntax names may be used in the syntax mate shown in FIG.

[0029] In the syntax configuration of BPH shown in Figure 5, the Description column indicates how each syntax is coded. Also, ue(v) indicates an unsigned zeroth-order exponential Golomb code, and u(n) indicates an n-bit flag.

[0030] The BPH includes at least a control signal (mdu_face_count_minus1) that specifies the number of elementary faces included in the basic mesh patch.

[0031] The BPH also includes at least a control signal (mdu_subdivision_method_id) that specifies the type of subdivision method for the base mesh for each base patch.

[0032] The BPH may also include a control signal (mdu_subdivision_num_method_id) that specifies the type of subdivision number generation method for each basic mesh patch. For example, when mdu_subdivision_num_method_id=0, it may be defined that the subdivision number of the base surface is generated by the predicted division residual, and when mdu_subdivision_num_method_id=1, it may be defined that the subdivision number of the base surface is generated recursively.

[0033] When generating the number of subdivisions of the base face by the prediction division residuals, the BPH may include a control signal (mdu_subdivision_residuals) that specifies the prediction division residuals of the base face for each index i (i=0, . . . , mdu_face_count_minus1).

[0034] The BPH may include a control signal (mdu_max_depth) for identifying an upper limit on the number of subdivisions to perform recursively for each base mesh patch when recursively generating the number of subdivisions of the base surface.

[0035] The BPH may include a control signal (mdu_subdivision_flag) that specifies whether or not to recursively sub-divide a base face for each index i (i=0,...,mdu_face_count_minus1) and j (j=0,...,mdu_subdivision_depth_index).

[0036] As shown in FIG. 6, the basic mesh decoding unit 202 includes a separation unit 202A, an intra decoding unit 202B, a mesh buffer unit 202C, a connection information decoding unit 202D, and an inter decoding unit 202E.

[0037] The separator 202A is configured to classify the base mesh bitstream into a bitstream of I-frames (reference frames) and a bitstream of P-frames.

[0038] (Intra decoding unit 202B) The intra decoder 202B is configured to decode the vertex coordinates and connection information of the I frame from the bit stream of the I frame, for example, using Draco described in Non-Patent Document 2.

[0039] FIG. 39 is a diagram illustrating an example of functional blocks of the intra decoding unit 202B.

[0040] As shown in FIG. 39, the intra decoding unit 202B includes a separation unit 202A, an arbitrary intra decoding unit 202B1, and an alignment unit 202B2.

[0041] The arbitrary intra decoder 202B1 is configured to decode the coordinates and connectivity information of the unordered vertices of the I-frame from the bit stream of the I-frame using any method including Draco described in Non-Patent Document 2.

[0042] The sorting unit 202B2 is configured to output the vertices by sorting the unordered vertices into a predetermined order.

[0043] As the predetermined order, for example, the Morton code order or the raster scan order may be used.

[0044] Also, multiple vertices with the same coordinates, i.e., overlapping vertices, may be combined into a single vertex and then rearranged in a predetermined order.

[0045] The mesh buffer unit 202C is configured to store the vertex coordinates and connection information of the I frame decoded by the intra decoding unit 202B.

[0046] The connection information decoding unit 202D is configured to convert the connection information of the I frame extracted from the mesh buffer unit 202C into connection information of a P frame.

[0047] The inter decoding unit 202E is configured to decode the coordinates of the vertices of the P frame by adding the coordinates of the vertices of the I frame retrieved from the mesh buffer unit 202C to the motion vectors decoded from the bit stream of the P frame.

[0048] In this embodiment, as shown in Fig. 7, there is a correspondence between the vertices of the base mesh of the P frame and the vertices of the base mesh of the I frame (reference frame). Here, the motion vector decoded by the inter decoding unit 202E is a difference vector between the coordinates of the vertices of the base mesh of the P frame and the coordinates of the vertices of the base mesh of the I frame.

[0049] (Inter-decoding unit 202E) FIG. 8 is a diagram illustrating an example of functional blocks of the inter decoding unit 202E.

[0050] As shown in FIG. 8, the inter decoding unit 202E includes a motion vector residual decoding unit 202E1, a motion vector buffer unit 202E2, a motion vector prediction unit 202E3, a motion vector calculation unit 202E4, and an adder 202E5.

[0051] The motion vector residual decoding unit 202E1 is configured to generate a motion vector residual (MVR) from a bit stream of a P frame.

[0052] Here, MVR is a motion vector residual indicating the difference between MV (Motion Vector) and MVP (Motion Vector Prediction). MV is a difference vector (motion vector) between the coordinates of the vertex of the corresponding I frame and the coordinates of the vertex of the corresponding P frame. MVP is a predicted value of the MV of the target vertex using MV (predicted value of the motion vector).

[0053] The motion vector buffer unit 202E2 is configured to sequentially store the MVs output by the motion vector calculation unit 202E4.

[0054] The motion vector prediction unit 202E3 is configured to obtain a decoded MV from the motion vector buffer unit 202E2 for a vertex connected to the vertex to be decoded, and output an MVP of the vertex to be decoded using all or part of the obtained decoded MV, as shown in Figure 9.

[0055] The motion vector calculation unit 202E4 is configured to add the MVR generated by the motion vector residual decoding unit 202E1 and the MVP output from the motion vector prediction unit 202E3, and output the MV of the vertex to be decoded.

[0056] The adder 202E5 is configured to add the coordinates of a vertex corresponding to the vertex to be decoded, obtained from the decoded basic mesh of a corresponding I frame (reference frame), to the motion vector MV output from the motion vector calculation unit 202E3, and output the coordinates of the vertex to be decoded.

[0057] Hereinafter, each component of inter decoding unit 202E will be described in detail.

[0058] FIG. 10 shows a flowchart illustrating an example of the operation of the motion vector prediction unit 202E3.

[0059] As shown in FIG. 10, in step S1001, the motion vector prediction unit 202E3 sets MVP and N to 0.

[0060] In step S1002, the motion vector prediction unit 202E3 obtains a set of MVs of vertices around the vertex to be decoded from the motion vector buffer unit 202E2, identifies vertices for which subsequent processing has not been completed, and transitions to No, or transitions to Yes if subsequent processing has been completed for all vertices.

[0061] In step S1003, if the MV of the vertex to be processed has not been decoded, the motion vector prediction unit 202E3 transitions to No, and if the MV of the vertex to be processed has been decoded, the motion vector prediction unit 202E3 transitions to Yes.

[0062] In step S1004, the motion vector prediction unit 202E3 adds MV to MVP and adds 1 to N.

[0063] In step S1005, if N is greater than 0, the motion vector prediction unit 202E3 outputs the result of dividing MVP by N, and if N is 0, outputs 0, and the process ends.

[0064] That is, the motion vector prediction unit 202E3 is configured to output the MVP to be decoded by averaging the decoded motion vectors of vertices around the vertex to be decoded.

[0065] The motion vector prediction unit 202E3 may be configured to set the MVP to 0 when the set of decoded motion vectors is an empty set.

[0066] The motion vector calculation unit 202E4 may be configured to calculate the MV of the vertex to be decoded from the MVP output by the motion vector prediction unit 202E3 and the MVR generated by the motion vector residual decoding unit 202E1, using equation (1).

[0067] MV(k)=MVP(k)+MVR(k) … (1) where k is the index of the vertex. MV, MVR and MVP are vectors with x, y and z components.

[0068] According to this configuration, since only the MVR is encoded instead of the MV using the MVP, it is expected to have the effect of improving the encoding efficiency.

[0069] The adder 202E5 is configured to calculate the coordinates of a vertex by adding the MV of the vertex calculated by the motion vector calculation unit 202E4 to the coordinates of the vertex in the reference frame corresponding to the vertex, and to leave the connectivity information (Connectivity) as it is in the reference frame.

[0070] Specifically, the adder 202E5 calculates the coordinate v' of the kth vertex using the formula (2). i (k) may be calculated.

[0071] v' i (k)=v' j (k) + MV(k) … (2) where v' i (k) is the coordinate of the kth vertex to be decoded in the frame to be decoded, and v' j (k) is the coordinate of the k-th decoded vertex of the reference frame, and MV(k) is the k-th MV of the frame to be decoded, where k=1, 2, . . . , K.

[0072] Moreover, the connection information of the frame to be decoded is made the same as the connection information of the reference frame.

[0073] Note that since the motion vector prediction unit 202E3 calculates the MVP using a decoded MV, the order of decoding affects the MVP.

[0074] The order of the decoding is the order of the vertices of the base mesh in the reference frame. In general, if a decoding method is used that uses a certain repetitive pattern to increase the number of base faces one by one from the starting edge, the order of the vertices of the decoded base mesh is determined during the decoding process.

[0075] For example, the motion vector prediction unit 202E3 may use an Edgebreaker to determine the order of decoding vertices in the base mesh of the reference frame.

[0076] According to this configuration, since MVs from a reference frame are encoded instead of vertex coordinates, it is expected that the encoding efficiency can be improved.

[0077] (Modification 1 of the inter-decoding unit 202E) The MVP calculated in the flowchart shown in FIG. 10 is calculated as a simple average of surrounding decoded MVs, but it may be calculated as a weighted average.

[0078] In other words, the motion vector prediction unit 202E3 may be configured to output a predicted value of the motion vector to be decoded by taking a weighted average of the decoded motion vectors of the vertices around the vertex to be decoded, with a weight according to the distance between the vertex to be decoded and the vertices of the reference frame corresponding to the vertex to be decoded and the vertices around the vertex to be decoded.

[0079] In addition, the motion vector prediction unit 202E3 may be configured to output a predicted value of the motion vector to be decoded by taking a weighted average of a portion of the decoded motion vectors of vertices around the vertex to be decoded, with a weight according to the distance between the vertex to be decoded and the vertices of the reference frame corresponding to the vertex to be decoded and the vertices around the vertex to be decoded.

[0080] In this first modification, the motion vector prediction unit 202E3 of the inter decoding unit 202E is configured to calculate the MVP in the following procedure.

[0081] First, the motion vector predictor 202E3 is configured to calculate weights.

[0082] FIG. 11 is a flowchart showing an example of the operation of calculating the sum Total_D of the distances to the surrounding vertices that have already been decoded.

[0083] As shown in FIG. 11, in step S1101, the motion vector prediction unit 202E3 sets 0 to Total_D.

[0084] Step S1102 is the same as step S1002.

[0085] Step S1103 is the same as step S1003.

[0086] In step S1104, the motion vector prediction unit 202E3 adds e(k) to Total_D.

[0087] That is, the motion vector prediction unit 202E3 refers to a set of vertices around the vertex to be decoded, and adds the distances of vertices that have already been decoded.

[0088] In this first modification, the motion vector prediction unit 202E3 is configured to calculate the weights using the distances in a reference frame in which the correspondences between vertices are known.

[0089] That is, e(k) in step S1104 of FIG. 11 is the distance between corresponding vertices in the reference frame.

[0090] Then, the motion vector prediction unit 202E3 may be configured to calculate the weight w(k) according to equations (3) and (4).

[0091]

number

[0092] The motion vector prediction unit 202E3 may be configured to set the weight according to a predetermined rule depending on the distance.

[0093] For example, the motion vector prediction unit 202E3 may be configured to set the weight to 1 if e(k) is smaller than a threshold TH1, to set the weight to 0.5 if e(k) is smaller than a threshold TH2, and to set the weight to 0 otherwise (no weight is used).

[0094] According to this configuration, by increasing the weight when the distance to the vertex to be decoded is short, it is expected that the MVP can be calculated with higher accuracy.

[0095] Second, the motion vector prediction unit 202E3 is configured to refer to the MVP.

[0096] FIG. 12 shows a flowchart illustrating an example of the operation of calculating the MVP using the weighted average.

[0097] As shown in FIG. 12, in step S1201, the motion vector prediction unit 202E3 sets MVP and N to 0.

[0098] Step S1202 is the same as step S1002.

[0099] Step S1203 is the same as step S1003.

[0100] In step S1204, the motion vector prediction unit 202E3 adds w(k)×MV(k) to MVP, and adds 1 to N.

[0101] Step S1205 is the same as step S1005.

[0102] Alternatively, the motion vector prediction unit 202E3 may be configured to calculate the MVP according to equation (5).

[0103]

number

[0104] According to this configuration, since it is possible to calculate a more accurate MVP by using a weighted average, it is expected that the coding efficiency can be improved by reducing the MVR value and concentrating it around zero.

[0105] (Modification 2 of the inter-decoding unit 202E) In this second modification, the motion vector prediction unit 202E3 is configured to select one MV rather than calculating an MVP using a plurality of surrounding MVs.

[0106] In other words, the motion vector prediction unit 202E3 may be configured to select the MV of the nearest vertex from among the decoded MVs stored in the motion vector buffer unit 202E2 as the MV of the vertex connected to the vertex to be decoded.

[0107] Here, the motion vector prediction unit 202E3 may be configured to construct a candidate list consisting of MVs of vertices connected to the vertex to be decoded from among the decoded MVs stored in the motion vector buffer unit 202E2, and to select a motion vector from the candidate list based on an index decoded from the bitstream of the P frame (the frame to be decoded).

[0108] FIG. 13 shows a flowchart illustrating an example of an operation for selecting an MV as an MVP from a set of candidate MVs.

[0109] As shown in FIG. 13, in step S1301, the motion vector prediction unit 202E3 decodes the list ID from the bit stream of the P frame.

[0110] In step S1302, the motion vector prediction unit 202E3 selects, from among the candidate MVs, an MV to which a list ID is to be assigned as an MVP.

[0111] In the set of candidate MVs in FIG. 13, the surrounding MVs that have already been decoded and the MVs calculated by combining them are arranged in a certain order.

[0112] FIG. 14 shows a flowchart illustrating an example of the operation of creating such a set of candidate MVs.

[0113] As shown in FIG. 14, in step S1401, the motion vector prediction unit 202E3 refers to a set of MVs of vertices around the vertex to be decoded, and determines whether processing for all vertices around the vertex to be decoded has been completed.

[0114] If such processing is completed, the operation ends, and if such processing is not completed, the operation proceeds to step S1402.

[0115] In step S1402, the motion vector prediction unit 202E3 determines whether or not the MV of the target vertex has been decoded.

[0116] If the MV has been decoded, the operation proceeds to step S1403; if the MV has not been decoded, the operation returns to step S1401.

[0117] In step S1403, the motion vector prediction unit 202E3 determines whether or not the MV overlaps with another decoded MV.

[0118] If there is an overlap, the operation returns to step S1401; if there is no overlap, the operation proceeds to step S1404.

[0119] In step S1404, the motion vector prediction unit 202E3 determines a list ID to be assigned to the MV, and in step S1405, includes the MV in a set of candidate MVs.

[0120] In addition, in FIG. 14, when determining the list ID, the motion vector prediction unit 202E3 may increase the list ID by one in sequence, or may determine the list ID in the order of the distance between the vertex to be decoded in the reference frame and the vertex corresponding to vertex k (e(k) in equation (3)).

[0121] According to this configuration, selecting one of the candidate MVs as the MVP may be closer to the MV than the average in some cases, and in such cases, it is expected to have the effect of improving the coding efficiency.

[0122] Furthermore, the motion vector prediction unit 202E3 may be configured to add an MV obtained by averaging consecutive MV0 and MV1 from among the above-mentioned candidate MVs as a new candidate MV to the list. The motion vector prediction unit 202E3 adds such an MV after MV0 and MV1, as shown in Table 1.

[0123] [Table 1] According to this configuration, it is expected that the effect of increasing the possibility that the selected candidate MV is closer to the MV of the vertex to be decoded can be achieved.

[0124] Furthermore, the motion vector prediction unit 202E3 may be configured to select the MV of the nearest vertex from the set of candidate MVs without encoding the list ID. With this configuration, it is expected that the encoding efficiency can be further improved.

[0125] (Modification 3 of the inter-decoding unit 202E) In the above-described embodiment and modified examples 1 and 2, the surrounding vertices are vertices connected to the vertex to be decoded.

[0126] In contrast to this, in the present modified example 3, the motion vector predictor 202E3 is configured to calculate the MVP by parallelogram prediction, that is, by using vertices that are not directly connected to the vertex to be decoded.

[0127] As shown in FIG. 15, in parallelogram prediction, a vertex D on the opposite side of a decoded face having a shared edge BC with a vertex A to be decoded is also used.

[0128] Furthermore, the shared edges of the vertex A to be decoded are CE and BG in addition to AB. Therefore, in parallelogram prediction, vertices F and H can also be used in a similar manner.

[0129] For example, the motion vector prediction unit 202E3 may be configured to calculate MVP according to equation (6) using the plane BCD shown in FIG.

[0130] MVP = MV(B) + MV(C) - MV(D) … (6) Here, MV(X) is the motion vector of vertex X, and MVP is the motion vector prediction value of vertex A to be decoded.

[0131] Furthermore, when there are a plurality of shared edges as described above, the motion vector prediction unit 202E3 may average the MVPs of each edge, or may select the face whose center of gravity is closest to the face.

[0132] (Modification 4 of the inter-decoding unit 202E) In this modification, the MVR generated by the motion vector residual decoding unit 202E1 is not directly converted, but the quantization width when expressing the MVR as an integer is controlled.

[0133] In this modification, the motion vector residual decoding unit 202E1 is configured to decode adaptive_mesh_flag, adaptive_bit_flag, and a precision control parameter as control information for controlling the quantization width of MVR.

[0134] That is, the motion vector residual decoding unit 202E1 is configured to decode the adaptive_mesh_flag of the entire basic mesh and the adaptive_bit_flag of each basic patch.

[0135] Here, adaptive_mesh_flag and adaptive_bit_flag are flags indicating whether or not to adjust the quantization width of the above-mentioned MVR, and take the value of either 0 or 1.

[0136] Here, the motion vector residual decoding unit 202E1 decodes adaptive_bit_flag only when adaptive_mesh_flag is valid (ie, 1).

[0137] Furthermore, when adaptive_mesh_flag is invalid (ie, 0), the motion vector residual decoding unit 202E1 regards adaptive_bit_flag as invalid (ie, 0).

[0138] FIG. 16 shows a flowchart illustrating an example of an operation for controlling the quantization width of the decoded MVR from the control information adaptive_mesh_flag, adaptive_bit_flag, and precision control parameter generated by decoding the basic mesh bit stream.

[0139] As shown in FIG. 16, in step S1601, the motion vector prediction unit 202E3 determines whether adaptive_mesh_flag is 0 or not.

[0140] If it is determined that adaptive_mesh_flag is 0 for the entire mesh, this operation ends.

[0141] On the other hand, if it is determined that adaptive_mesh_flag is 1 for the entire mesh, the operation proceeds to step S1602.

[0142] In step S1602, the motion vector prediction unit 202E3 determines whether or not there is an unprocessed patch in the frame.

[0143] In step S1603, the motion vector prediction unit 202E3 determines whether or not adaptive_mesh_flag decoded for each patch is 0.

[0144] If it is determined that adaptive_mesh_flag is 0, the operation returns to step S1601.

[0145] On the other hand, if it is determined that adaptive_mesh_flag is 1, the operation proceeds to step S1604.

[0146] In step S1604, the motion vector prediction unit 202E3 controls the quantization step size of the MVR based on a precision control parameter, which will be described later.

[0147] The MVR value with the quantization width controlled in this way is called "MVRQ (Motion Vector Residual Quantization)".

[0148] Here, the motion vector prediction unit 202E3 may be configured to use the quantization width of the MVR corresponding to the quantization width control parameter generated by decoding the basic mesh bitstream, for example, by referring to a table such as Table 2.

[0149] [Table 2] According to this configuration, it is expected that the coding efficiency can be improved by controlling the quantization width of MVR. Furthermore, it is expected that the hierarchical mechanism of adaptive_mesh_flag at the mesh level and adaptive_mesh_flag at the patch level can minimize the wasted bits when the quantization width of MVR is not controlled.

[0150] (Modification 5 of the inter-decoding unit 202E) If the MVR generated by the motion vector residual decoding unit 202E1 is not coded, an error occurs. In this fifth modification, in order to correct such an error, a discrete motion vector difference is coded.

[0151] 17, MVR can take values ​​of 1, 2, 4, and 8 in six directions of the x-axis, y-axis, and z-axis. An example of such encoding is shown in Tables 3 and 4.

[0152] Also, MVR encoding may be performed using a combination of multiple directions. For example, correction may be performed in the order of 2 in the positive direction of the x-axis and 1 in the positive direction of the y-axis.

[0153] [Table 3]

[0154] [Table 4] According to this configuration, it is expected that the efficiency of coding discrete motion vector differences will be higher than that of MVR coding.

[0155] Hereinafter, further modifications of the inter decoding unit 202E will be described.

[0156] A further modification of the above-described inter-decoding unit 202E is configured to add the following functional blocks before implementing the above-described inter-decoding unit 202E.

[0157] Specifically, as shown in FIG. 18, the inter decoding unit 202E includes, in addition to the configuration shown in FIG. 8, an overlapping vertex searching unit 202E6, an overlapping vertex determining unit 202E7, a motion vector obtaining unit 202E8, an all skip mode single, and a skip mode single.

[0158] Here, the All skip mode signal is at the beginning of the bitstream of a P frame and has at least two values, being one bit or more than one bit.

[0159] One of them (when the All skip mode signal indicates Yes, e.g., 1) is a signal to not decode motion vectors of all duplicated vertices of the P frame from the bitstream and to copy the motion vectors of the duplicated vertices.

[0160] The other (when the All skip mode signal indicates No, for example, 0) is a signal that performs different processing at each vertex of the P frame. Furthermore, the other may have another value. For example, the other is a single signal that does not perform processing in the motion vector acquisition unit 202E8 for the motion vectors of all overlapping vertices, but performs processing similar to that of the inter decoding unit 202E shown in FIG. 8.

[0161] Here, when the All skip mode signal indicates No, the Skip mode signal has two values ​​for each overlapping vertex, and is 1 bit.

[0162] The Skip mode signal is a signal that, when the All skip mode signal indicates Yes (for example, when it is 1), the motion vector of the vertex is not decoded from the bitstream, and the motion vector of the duplicated vertex is copied.

[0163] When the All skip mode signal indicates No (for example, when it is 0), the motion vector acquisition unit 202E8 does not perform processing on the motion vector of the vertex, and the same processing as that of the inter decoding unit 202E shown in FIG. 8 is performed.

[0164] The above-mentioned skip mode signal may be decoded directly from the bitstream, or data identifying an overlapped vertex (e.g., an index of the overlapped vertex) that performs processing similar to that of the inter decoding unit 202E shown in Figure 8 may be decoded from the bitstream, and the skip mode signal may be calculated from such data.

[0165] Furthermore, as shown in FIG. 38, instead of calculating the Skip mode signal, the motion vector decoding method for the vertex may be determined in the same manner as described above by using data identifying the overlapping vertex (e.g., an index of the overlapping vertex) that performs processing similar to that of the inter decoding unit 202E shown in FIG. 8 described above.

[0166] The overlapping vertex search unit 202E6 is configured to search for the index of a vertex having matching coordinates (hereinafter, referred to as an overlapping vertex) from the geometric information of the basic mesh of the decoded reference frame, and store the index in a buffer (not shown).

[0167] Specifically, the input to the overlapping vertex search unit 202E6 is the index (in decoding order) and position coordinates of each vertex of the basic mesh of the decoded reference frame.

[0168] The output of the duplicated vertex search unit 202E6 is a list of pairs of the index (vindex0) of a vertex where a duplicated vertex exists and the index (vindex1) of the duplicated vertex. Here, the list of pairs is stored in the buffer repVert in the order of index0.

[0169] Furthermore, since the vertex of vindex1 is decoded before vindex0, the relationship vindex0>vindex1 holds.

[0170] In addition, as a method of identifying duplicate vertices in the base mesh of the reference frame, for vertices where duplicate vertices exist, a special signal is used to decode the index of the duplicate vertex, instead of the position coordinates. By using such a special signal, the pair of the index of the corresponding vertex and the index of the duplicate vertex can be stored in the decoding order.

[0171] The duplicated vertex determination unit 202E7 is configured to determine whether or not the corresponding vertex includes a duplicated vertex among the decoded vertices.

[0172] Here, if the index of the corresponding vertex is among the indexes of vertices that have a duplicated vertex, the duplicated vertex discrimination unit 202E7 determines that the decoded vertices contain a duplicated vertex. Note that since the corresponding vertex comes in the decoding order, the above-mentioned search is not necessary.

[0173] Here, if the overlapping vertex determination unit 202E7 determines that no overlapping vertex exists for the corresponding vertex, the same process as that of the inter decoding unit 202E shown in FIG. 8 is performed.

[0174] The motion vector acquisition unit 202E8 is configured to acquire the motion vector of a vertex having the same index as the overlapping vertex from the motion vector buffer unit 202E2 that stores the decoded motion vector when a duplicate vertex of the corresponding vertex exists, when the All skip mode signal indicates Yes, or when the All skip mode signal indicates No and the Skip mode signal of the corresponding vertex indicates Yes, and to set it as the motion vector of the corresponding vertex.

[0175] Here, when the All skip mode signal indicates No and the Skip mode signal of the corresponding vertex indicates No, the same process as that of the inter decoding unit 202E shown in FIG. 8 is performed instead of the motion vector acquisition unit 202E8.

[0176] According to this configuration, it is expected that the effect of reducing the decoding calculation and the amount of code of the motion vector for the vertices having overlapping vertices can be achieved.

[0177] In a further modification of the above-described inter decoding unit 202E, the inter decoding unit 202E obtains, from a decoded base mesh of the reference frame, a correspondence relationship between the vertices of the reference frame and the vertices of the frame to be decoded.

[0178] The inter-decoding unit 202E is configured to, based on this correspondence, make the vertex connection information of the frame to be decoded the same as the decoded vertex connection information of the reference frame without encoding the vertex connection information.

[0179] In addition, the inter-decoding unit 202E divides the basic mesh of the frame to be decoded into two types of regions based on the signal in the decoding order of the vertices of the reference frame. The first region is decoded using inter processing, and the second region is decoded using intra processing.

[0180] The above-mentioned area is defined as an area formed by a plurality of consecutive vertices in the decoding order when decoding a basic mesh of a reference frame.

[0181] In addition, the following two implementations are assumed for the means of decoding the coordinates of the vertices of the base mesh of the frame to be decoded using a signal. (Measure 1) In means 1, the signals are vertex_idx1, vertex_idx2 and intra_flag.

[0182] Here, vertex_idx1 and vertex_idx2 are indices (vertex indices) of the vertices in the decoding order, and intra_flag is a flag indicating whether the decoding method is the inter-decoding method or the intra-decoding method. There may be a plurality of such signals.

[0183] That is, vertex_idx1 and vertex_idx2 are vertex indices that define the start position and end position of the above-mentioned partial region (first region and second region). (Measure 2) Method 2 is based on the premise that the Edgebreaker decodes the connection information of the base mesh in the reference frame, and the decoding order of the vertex coordinates is the order determined by the Edgebreaker.

[0184] FIG. 19 is a diagram showing an example of an operation for determining connection information and the order of vertices using Edgebreaker.

[0185] In FIG. 19, arrows indicate the decoding order of connection information, numbers indicate the decoding order of vertices, and arrows of the same line type define the same area.

[0186] In the means 2, the signal is only intra_flag, which is a flag indicating whether the decoding method is an inter-decoding method or an intra-decoding method.

[0187] That is, in the means 2, the inter decoding unit 202E is configured to divide into a first region and a second region by using an Edgebreaker.

[0188] <Subdivision section 203> The subdivision unit 203 is configured to generate and output added subdivision vertices and their connection information from the basic mesh decoded by the basic mesh decoding unit 202 using a subdivision method indicated by the control information.

[0189] Here, the basic mesh, the added subdivision vertices, and their connection information are collectively referred to as a "subdivision mesh."

[0190] The subdivision unit 202 is configured to identify the type of subdivision method from subdivision_method_id, which is control information generated by decoding the basic mesh bit stream.

[0191] The subdivision unit 202 will now be described with reference to FIGS. 3A and 3B.

[0192] 3A and 3B are diagrams for explaining an example of an operation for generating subdivision vertices from a basic mesh.

[0193] FIG. 3A is a diagram showing an example of a base mesh composed of five vertices.

[0194] Here, the subdivision may be performed, for example, by using a mid-edge division method in which the midpoints of the sides of each basic face are connected to each other, resulting in a basic face being divided into four faces.

[0195] Figure 3B shows an example of a subdivision mesh obtained by dividing a base mesh consisting of five vertices, in which eight subdivision vertices (white circles) are generated in addition to the original five vertices (black circles).

[0196] By decoding the displacement amount for each subdivision vertex thus generated by the displacement amount decoder 206, it is possible to expect improvement in coding performance.

[0197] Also, a different subdivision method may be applied to each patch. This allows the displacement decoded by the displacement decoder 206 to be adaptively changed for each patch, which is expected to improve coding performance. Information on the divided patches is received as patch_id, which is control information.

[0198] The subdivision section 203 will be described below with reference to Fig. 20. Fig. 21 is a diagram showing an example of functional blocks of the subdivision section 203.

[0199] As shown in FIG. 21, the subdivision section 203 has a basic mesh subdivision section 203A and a subdivision mesh adjustment section 203B.

[0200] (Basic mesh refinement section 203A) The basic mesh subdivision unit 203A is configured to calculate the number of divisions (number of subdivisions) for each basic surface and basic patch based on the input basic mesh and division information of the basic mesh, subdivide the basic mesh based on the number of divisions, and output the subdivision surface.

[0201] In other words, the basic mesh subdivision unit 203A may be configured to be able to change the above-mentioned number of divisions for each basic surface and basic patch.

[0202] Here, a base face is a face that constitutes a base mesh, and a base patch is a collection of several base faces.

[0203] In addition, the basic mesh subdivision unit 203A may be configured to predict the number of fine subdivisions of the base surface and calculate the number of subdivisions of the base surface by adding a predicted subdivision number residual to the predicted number of subdivisions of the base surface.

[0204] The basic mesh subdivision unit 203A may be configured to calculate the number of subdivisions of a basic surface based on the number of subdivisions of an adjacent basic surface of the basic surface.

[0205] The basic mesh subdivision unit 203A may be configured to calculate the number of subdivisions of a base surface based on the number of subdivisions of the base surface that has been stored immediately before.

[0206] The basic mesh subdivision unit 203A may be configured to generate vertices that divide the three sides that constitute the basic surface, and to connect the generated vertices to subdivide the basic surface.

[0207] As shown in FIG. 21, a basic mesh subdivision section 203A is followed by a subdivision mesh adjustment section 203B, which will be described later.

[0208] An example of the processing of the basic mesh subdivision section 203A will be described below with reference to FIGS.

[0209] FIG. 21 is a diagram showing an example of functional blocks of the basic mesh subdivision unit 203A, and FIG. 23 is a flowchart showing an example of the operation of the basic mesh subdivision unit 203A.

[0210] As shown in FIG. 21, the basic mesh subdivision unit 203A has a basic surface division number buffer unit 203A1, a basic surface division number reference unit 203A2, a basic surface division number prediction unit 203A3, an addition unit 203A4, and a basic surface division unit 203A5.

[0211] The basic surface division number buffer unit 203A1 stores division information of basic surfaces including the division number of the basic surface, and is configured to output the division information of the basic surface to the basic surface division number reference unit 203A2.

[0212] Here, the size of the basic surface division number buffer unit 203A1 may be set to 1, and the unit may be configured to output the division number of the basic surface that was stored immediately before to the basic surface division number reference unit 203A2.

[0213] That is, by setting the size of the basic surface division number buffer unit 203A1 to 1, it may be configured to refer to only the last decoded fine division number (the subdivision number decoded immediately before).

[0214] The basic surface division number reference unit 203A2 is configured to output a reference not possible to the basic surface division number prediction unit 203A3 when there is no adjacent basic surface to the basic surface to be decoded, or when there is an adjacent basic surface to the basic surface to be decoded but the number of divisions has not been determined.

[0215] On the other hand, when a base face adjacent to the base face to be decoded exists and the number of divisions is determined, the basic face division number reference unit 203A2 is configured to output the number of divisions to the basic face division number prediction unit 203A3.

[0216] The basic surface division number prediction unit 203A3 is configured to predict the division number (subdivision number) of a basic surface based on one or more input division numbers, and output the predicted division number (predicted division number) to the addition unit 203A4.

[0217] Here, the basic surface division number prediction unit 203A3 is configured to output 0 to the addition unit 203A4 when only reference impossible is input from the basic surface division number reference unit 203A2.

[0218] In addition, when one or more division numbers are input, the basic surface division number prediction unit 203A3 may be configured to generate a predicted division number using any of the statistical values ​​such as the average value, maximum value, minimum value, or mode of the input division numbers.

[0219] The basic face division number prediction unit 203A3 may be configured to generate the division number of the most adjacent face as the predicted division number when one or more division numbers are input.

[0220] The addition unit 203A4 is configured to output the division number obtained by adding the prediction division number residual decoded from the prediction residual bitstream and the prediction division number obtained from the basic surface division number prediction unit 203A3 to the basic surface division unit 203A5.

[0221] The basic surface division unit 203A5 is configured to finely divide the basic surface based on the number of divisions input from the addition unit 203A4.

[0222] FIG. 22 shows an example of a case where the basic surface is divided into nine parts. With reference to FIG. 22, the method of dividing the basic surface by the basic surface division unit 203A5 will be described.

[0223] The basic surface division unit 203A5 generates points A_1,…,A_(N-1) that divide the side AB forming the basic surface into N equal parts (N = 3).

[0224] Similarly, the basic surface division unit 203A5 also divides the sides BC and CA into N equal parts, and generates points B_1,…,B_(N-1) and C_1,…,C_(N-1) respectively.

[0225] Hereinafter, the points on the sides AB, BC, and CA are referred to as "side division points".

[0226] For all i (i = 1, 2,…, N-1), the basic surface division unit 203A5 generates the sides A_i B_(N-i), B_i C_(N-i), C_i A_(N-i), and generates N 2 fine division surfaces.

[0227] Next, with reference to FIG. 23, the processing procedure of the basic mesh division unit 203A will be described.

[0228] In step S2201, it is determined whether the re-division process for the last basic surface has been completed. If the process is completed, the process ends; otherwise, it proceeds to step S2202.

[0229] In step S2202, the basic mesh division unit 203A determines whether Depth < mdu_max_depth.

[0230] Here, Depth is a variable representing the current depth, with an initial value of 0, and mdu_max_depth represents the maximum depth determined for each basic surface.

[0231] If the condition in step S2202 is met, the process proceeds to step S2203; if the condition is not met, the process returns to step S2201.

[0232] In step S2203, the basic mesh subdivision unit 203A determines whether or not mdu_subdivision_flag is 1 at the current depth.

[0233] If the answer is Yes, the process returns to step S2201; if the answer is No, the process proceeds to step S2204.

[0234] In step S2204, the basic mesh subdivision unit 203A further subdivides all the subdivision surfaces within the basic surface.

[0235] Here, if the subdivision process has never been performed on the basic surface, the basic mesh subdivision unit 203A subdivides the basic surface.

[0236] The subdivision method is the same as that described in step S2204.

[0237] Specifically, if a basic surface has never been subdivided, the basic surface is subdivided as shown in FIG. 22. If the basic surface has been subdivided at least once, the subdivision surface is 2 In the example of FIG. 22, the face consisting of vertices A_2, B, and B_1 is further divided into N 2 Generate faces.

[0238] When the subdivision process is completed, the process proceeds to step S2205.

[0239] In step S2205, the basic mesh subdivision unit 203A adds 1 to Depth, and the processing procedure returns to step S2202.

[0240] (Fine division mesh adjustment unit 203B) Next, a specific example of the process performed by the finely divided mesh adjustment unit 203B will be described. An example of the process performed by the finely divided mesh adjustment unit 203B will be described below with reference to FIGS.

[0241] FIG. 24 is a diagram showing an example of functional blocks of the finely divided mesh adjustment unit 203B.

[0242] As shown in FIG. 24, the subdivision mesh adjustment unit 203B has an edge division point moving unit 701 and a subdivision surface division unit 702. (Edge division point moving unit 701) The edge division point moving unit 701 is configured to move an edge division point of a basic face to any of the edge division points of an adjacent basic face for an input initial subdivision face, and output a subdivision face.

[0243] Fig. 25 shows an example in which an edge division point on a basic face ABC is moved. For example, as shown in Fig. 25, the edge division point moving unit 701 may be configured to move an edge division point of the basic face ABC to an edge division point of the nearest adjacent basic face.

[0244] (Subdivision surface division part 702) The subdivision surface division unit 702 is configured to re-subdivide the input subdivision surface and output a decomposed subdivision surface.

[0245] FIG. 26 is a diagram showing an example of a case where subdivision is performed again on a subdivision surface X in a basic surface.

[0246] As shown in FIG. 26, the subdivision surface division unit 702 may be configured to generate a new subdivision surface within a base surface by connecting vertices constituting the subdivision surface to edge division points of an adjacent base surface.

[0247] FIG. 27 is a diagram showing an example of a case where the above-mentioned subdivision processing is performed on all subdivision surfaces.

[0248] The mesh decoding unit 204 is configured to generate and output a decoded mesh using the subdivision mesh generated by the subdivision unit 203 and the displacement amount decoded by the displacement amount decoding unit 206 .

[0249] Specifically, the mesh decoding unit 204 is configured to generate a decoded mesh by adding, to each subdivision vertex, a corresponding displacement amount, where information about which subdivision vertex each displacement amount corresponds to is indicated by control information.

[0250] The patch integration unit 205 is configured to integrate the decoded mesh generated by the mesh decoding unit 206 by the amount of a plurality of patches and output the integrated mesh.

[0251] Here, the patch division method is defined by the mesh encoding device 100. For example, the patch division method may be configured to calculate a normal vector for each basic face, select a basic face having the most similar normal vector among adjacent basic faces, combine both basic faces into the same patch, and repeat such a procedure for the next basic face in sequence.

[0252] The video decoding unit 207 is configured to decode the texture by video coding and output the texture. For example, the video decoding unit 207 may use HEVC in Non-Patent Document 1.

[0253] <Displacement Amount Decoding Unit 206> The displacement amount decoding unit 206 is configured to decode the displacement amount bitstream to generate and output the displacement amount.

[0254] FIG. 28 is a diagram showing an example of the amount of displacement for a certain subdivision vertex.

[0255] In the example of FIG. 3B, there are eight subdivision vertices, and therefore the displacement decoder 206 is configured to define eight displacements, each expressed as a scalar or vector, for each subdivision vertex.

[0256] The displacement amount decoding unit 206 will be described below with reference to Fig. 28. Fig. 28 is a diagram showing an example of functional blocks of the displacement amount decoding unit 206.

[0257] As shown in FIG. 28, the displacement amount decoding unit 206 has a decoding unit 206A, an inverse quantization unit 206B, an inverse wavelet transform unit 206C, an adder 206D, an inter prediction unit 206E, and a frame buffer 206F.

[0258] The decoding unit 206A is configured to decode and output the level value and the control information by performing variable length decoding on the received displacement bit stream. Here, the level value obtained by the variable length decoding is output to the inverse quantization unit 206B, and the control information is output to the inter prediction unit 206E.

[0259] An example of the configuration of a displacement amount bit stream will be described below with reference to Fig. 29. Fig. 29 is a diagram showing an example of the configuration of a displacement amount bit stream.

[0260] As shown in FIG. 29, first, the displacement bit stream may include a Displacement Parameter Set (DPS) which is a set of control information related to decoding of the displacement.

[0261] Secondly, the displacement bitstream may include a Displacement Patch Header (DPH), which is a collection of control information corresponding to a patch.

[0262] Third, the displacement bitstream may contain, next to the DPH, the encoded displacements that make up the patch.

[0263] As described above, the displacement bit stream has a configuration in which each coded displacement corresponds to one DPH and one DPS.

[0264] Note that the configuration in Fig. 29 is merely an example. As long as the DPH and DPS correspond to each coded displacement amount, elements other than those described above may be added as components of the displacement amount bit stream.

[0265] For example, as shown in FIG. 29, the displacement amount bit stream may include a sequence parameter set (SPS).

[0266] FIG. 30 is a diagram showing an example of a syntax configuration of a DPS.

[0267] In FIG. 30, the Descriptor column indicates how each syntax element is coded.

[0268] In addition, in FIG. 30, ue(v) means an unsigned zeroth-order exponential Golomb code, and u(n) means an n-bit flag.

[0269] When multiple DPSs exist, the DPS includes at least DPS id information (dps_displacement_parameter_set_id) for identifying each DPS.

[0270] Furthermore, the DPS may include a flag (interprediction_enabled_flag) that controls whether or not inter prediction is performed.

[0271] For example, it may be defined that inter prediction is not performed when interprediction_enabled_flag is 0, and that inter prediction is performed when interprediction_enabled_flag is 1. It may be defined that inter prediction is not performed when interprediction_enabled_flag is not included.

[0272] The DPS may include a flag (dct_enabled_flag) that controls whether or not to perform an inverse DCT.

[0273] For example, when the dct_enabled_flag is 0, it may be defined that the inverse DCT is not performed, and when the dct_enabled_flag is 1, it may be defined that the inverse DCT is performed. When the dct_enabled_flag is not included, it may be defined that the inverse DCT is not performed.

[0274] FIG. 31 is a diagram showing an example of the syntax structure of DPH.

[0275] As shown in FIG. 31, DPH at least includes DPS id information for specifying a DPS corresponding to each DPH.

[0276] The inverse quantization unit 206B is configured to generate and output a transform coefficient by inverse quantizing the level value decoded by the decoding unit 206A.

[0277] The inverse wavelet transform unit 206C is configured to generate and output a prediction residual by performing an inverse wavelet transform on the transform coefficient generated by the inverse quantization unit 206B.

[0278] (Inter prediction unit 206E) The inter prediction unit 206E is configured to generate and output a prediction displacement amount by performing inter prediction using the decoded displacement amount of the reference frame read from the frame buffer 206F.

[0279] The inter prediction unit 206E is configured to perform such inter prediction only when the interprediction_enabled_flag is 1.

[0280] The inter prediction unit 206E may perform inter prediction in the spatial domain or in the frequency domain. The inter prediction may perform bidirectional prediction using a reference frame in the past and a reference frame in the future in terms of time.

[0281] FIG. 28 illustrates an example of functional blocks of an inter prediction unit 206E when performing inter prediction in the spatial domain.

[0282] When performing inter prediction in the spatial domain, the inter prediction unit 206E may determine the predicted displacement amount of a subdivision vertex in the target frame by directly referring to the decoded displacement amount of the corresponding subdivision vertex in the reference frame.

[0283] Alternatively, the predicted displacement of a certain subdivision vertex in the target frame may be determined probabilistically according to a normal distribution with estimated mean and variance using the decoded displacements of corresponding subdivision vertices in multiple reference frames. In this case, the predicted displacement may be uniquely determined by the mean alone, with the variance set to zero.

[0284] Alternatively, the predicted displacement amount of a subdivision vertex in the target frame may be determined based on a regression curve estimated using the decoded displacement amounts of corresponding subdivision vertices in multiple reference frames, with time as the explanatory variable and displacement amount as the objective variable.

[0285] In the mesh coding device 100, the order of the decoded displacement amounts may be rearranged in order to improve coding efficiency for each frame.

[0286] In such a case, the inter prediction unit 206E may be configured to perform inter prediction on the reordered decoding displacement amounts.

[0287] The correspondence between the subdivision vertices of the reference frame and the frame to be decoded is indicated by control information.

[0288] FIG. 32 is a diagram illustrating an example of a correspondence relationship between subdivision vertices between a reference frame and a current frame for decoding when inter prediction is performed in the spatial domain.

[0289] FIG. 33 illustrates an example of functional blocks of the inter prediction unit 206E when performing inter prediction in the frequency domain.

[0290] When performing inter prediction in the frequency domain, the inter prediction unit 206E may determine predicted wavelet transform coefficients of a frequency in a frame to be decoded by directly referring to decoded wavelet transform coefficients of a corresponding frequency in a reference frame.

[0291] The inter prediction unit 206E may perform stochastic inter prediction according to a normal distribution with estimated mean and variance, using the decoded displacement amounts or decoded wavelet transform coefficients of the subdivision vertices in a plurality of reference frames.

[0292] The inter prediction unit 206E may perform inter prediction based on a regression curve estimated using the decoded displacement amounts or decoded wavelet transform coefficients of the subdivision vertices in a plurality of reference frames, with time as an explanatory variable and the displacement amount as a response variable.

[0293] The inter prediction unit 206E may be configured to perform bidirectional inter prediction using a temporally past reference frame and a future reference frame.

[0294] In the mesh coding device 100, the order of the decoded wavelet transform coefficients may be rearranged in order to improve the coding efficiency for each frame.

[0295] The frequency correspondence between the reference frame and the frame to be decoded is indicated by control information.

[0296] FIG. 34 is a diagram illustrating an example of a correspondence relationship in frequency between a reference frame and a current frame to be decoded when inter prediction is performed in the frequency domain.

[0297] In addition, when the subdivision unit 203 divides the base mesh into a plurality of patches, the inter prediction unit 206E is also configured to perform inter prediction for each divided patch. This increases the time correlation between frames, and is expected to improve coding performance.

[0298] The adder 206D receives the prediction residual from the inverse wavelet transform unit 206C and the prediction displacement amount from the inter prediction unit 206E.

[0299] The adder 206D is configured to add the prediction residual and the prediction displacement amount to calculate and output the decoded displacement amount.

[0300] The decoded displacement calculated by the adder 206D is also output to the frame buffer 206F.

[0301] The frame buffer 206F is configured to receive and store the decoded displacement amount from the adder 206D.

[0302] Here, the frame buffer 206F outputs the decoded displacement amount at the corresponding vertex in the reference frame in response to control information (not shown).

[0303] FIG. 35 is a flowchart showing an example of the operation of the displacement amount decoding unit 206.

[0304] As shown in FIG. 35, in step S3501, the displacement decoding unit 206 determines whether or not this process has been completed for all patches.

[0305] If Yes, the operation ends, and if No, the operation proceeds to step S3502.

[0306] In step S3502, the displacement decoding unit 206 performs inverse DCT, and then performs inverse quantization and inverse wavelet transform on the patch to be decoded.

[0307] In step S3503, the displacement decoding unit 206 determines whether or not the interpretation_enabled flag is 1.

[0308] If yes, the operation proceeds to step S3504; if no, the operation returns to step S3501.

[0309] In step S3504, the displacement decoding unit 206 performs the above-mentioned inter prediction and addition.

[0310] <Variation 1> Hereinafter, with reference to FIG. 36, a first modification of the first embodiment will be described, focusing on differences from the first embodiment.

[0311] FIG. 36 is a diagram showing an example of functional blocks of the displacement amount decoding unit 206 according to the present first modification.

[0312] As shown in FIG. 36, the displacement amount decoding unit 206 according to the present first modification includes an inverse DCT unit 206G subsequent to the decoding unit 206A, that is, between the decoding unit 206A and the inverse quantization unit 206B.

[0313] That is, in the present first modification, the inverse quantization unit 206B is configured to generate a prediction residual by performing an inverse wavelet transform on the level values ​​output from the inverse DCT unit 202G.

[0314] <Variation 2> Hereinafter, the second modification of the first embodiment will be described with reference to FIG. 37, focusing on the differences from the first embodiment.

[0315] As shown in FIG. 37, the displacement decoding unit 206 according to the present second modification includes a video decoding unit 2061, an image developing unit 2062, an inverse quantization unit 2063, and an inverse wavelet transformation unit 2064.

[0316] The video decoding unit 2061 is configured to decode the received displacement amount bit stream by video coding, and output a video.

[0317] For example, the video decoding unit 2061 may use HEVC in Non-Patent Document 1.

[0318] Furthermore, the video decoding unit 2061 may use a video encoding method in which a motion vector is always set to 0. For example, the video decoding unit 2061 may always set a motion vector of HEVC to 0 and always use inter prediction at the same position.

[0319] Furthermore, the video decoding unit 2061 may use a video encoding method in which conversion is always skipped. For example, the video decoding unit 2061 may always perform HEVC conversion in a conversion skip mode and use a video encoding method without conversion.

[0320] The image development unit 2062 is configured to develop the video decoded by the video decoding unit 2061 as a level value for each image (frame) and output it.

[0321] In such a development method, the image development unit 2062 can specify it by calculating backwards from the arrangement of the level values ​​in the image indicated by the control information.

[0322] The image development unit 2062 may arrange the level values ​​in the image, for example, in the order of raster operation, from high frequency components to low frequency components.

[0323] The inverse quantization unit 2063 is configured to inversely quantize the level values ​​generated by the image development unit 2062 to generate and output transformation coefficients.

[0324] The inverse wavelet transform unit 2064 is configured to perform an inverse wavelet transform on the transform coefficients generated by the inverse quantization unit 2063, thereby generating and outputting a decoded displacement amount.

[0325] The above-mentioned mesh encoding device 100 and mesh decoding device 200 may be realized as a program that causes a computer to execute each function (each step). [Industrial Applicability]

[0326] According to this embodiment, for example, it is possible to improve the overall service quality in video communication, which makes it possible to contribute to Goal 9 of the Sustainable Development Goals (SDGs) led by the United Nations, which is to "build resilient infrastructure, promote sustainable industrialization and foster innovation." [Explanation of symbols]

[0327] 1. Mesh processing system 100...Mesh coding device 200…Mesh decoding unit 201…Demultiplexer 202...Basic mesh decoding unit 202A…Separation part 202B... Intra decoding unit 202B1...Optional intra-decoding unit 202B2…Alignment section 202C…Mesh buffer section 202D…Connection information decoding unit 202E…Inter-decoding section 202E1...Motion vector decoding unit 202E2...Motion vector buffer unit 202E3...Motion vector prediction unit 202E4...Motion vector calculation unit 202E5…Adder 202E6…Duplicate vertex search unit 202E7…Duplicate vertex discrimination unit 202E8...Motion vector acquisition unit 203…Subdivision part 203A…Basic mesh refinement section 203A1...Basic face division number buffer section 203A2…Basic surface division number reference section 203A3...Basic surface division number prediction unit 203A4…Addition section 203A5…Basic surface division part 203B…Subdivision mesh adjustment section 204…Mesh decoding unit 205…Patch Integration Department 206...Displacement amount decoding unit 206A…Decoding section 206B, 2063...Dequantization section 206C, 2064...Inverse wavelet transform section 206D…Adder 206E…Inter prediction section 206F…Frame buffer 206G…Reverse DCT section 2062…Image development section 207, 2061...Video decoding section

Claims

1. A mesh decoding device, comprising: a displacement amount decoding unit configured to decode the displacement amount bitstream to generate and output a displacement amount; The displacement amount decoding unit a video decoding unit configured to output a video by decoding the displacement bitstream by video coding; an image development unit configured to develop the video as a level value for each image and output the level value; an inverse quantization unit configured to inverse quantize the level values ​​to generate transform coefficients; an inverse wavelet transform unit configured to generate the displacements by performing an inverse wavelet transform on the transform coefficients.

2. The mesh decoding device according to claim 1, wherein the video decoding unit is configured to output video by decoding using a video coding method in which a motion vector is always set to zero.

3. 3. The mesh decoding device according to claim 1, wherein the video decoding unit is configured to output video by decoding using a video encoding method in which conversion is always skipped.

4. A mesh decoding method, comprising: outputting a video by decoding the displacement bitstream according to a video coding scheme; generating level values ​​by expanding the video image by image; generating transform coefficients by inverse quantizing the level values; and generating displacements by performing an inverse wavelet transform on the transform coefficients.

5. A program for causing a computer to function as a mesh decoding device, comprising: The mesh decoding device comprises: a displacement amount decoding unit configured to decode the displacement amount bitstream to generate and output a displacement amount; The displacement amount decoding unit a video decoding unit configured to output a video by decoding the displacement bitstream through video coding; a decoding unit configured to output a level value by expanding the video for each image; an inverse quantization unit configured to inverse quantize the level values ​​to generate transform coefficients; an inverse wavelet transform unit configured to generate the displacement amount by performing an inverse wavelet transform on the transform coefficients.

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