3D Mesh Patch Correction Vector Signaling for Video Coding
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Solution Overview
Problem
The process of creating 2D patches from 3D data in video encoding and subsequent reconstruction back to 3D space introduces small shifts due to quantization errors, insufficient bit depth, resolution, and compression artefacts, leading to low objective quality scores and negatively affecting encoder performance.
Innovation Solution
The method involves deriving and signaling an error vector describing the shift between reconstructed and original 3D data, which is used to correct the patch locations and orientations during the decoding process, thereby improving the accuracy of 3D mesh reconstruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If 3D mesh is processed into 2D patches and reconstructed back to 3D, then compression efficiency is improved, but reconstruction accuracy deteriorates due to quantization errors and compression artifacts
Solution Approach 1:
The patent calculates correction vectors during the encoding process (before transmission) by comparing original 3D mesh data with reconstructed 3D mesh data. These correction vectors are then transmitted along with the bitstream to be applied during decoding, effectively compensating for quantization errors before they affect final reconstruction quality.
Solution Approach 2:
The patent implements a feedback mechanism where the encoder computes correction vectors based on the difference between original and reconstructed mesh data, transmits these corrections via the bitstream, and the decoder applies them to correct the reconstruction. This closed-loop feedback system continuously refines the reconstruction accuracy while maintaining compression efficiency.
2Quantity of substance
If quantization and compression are applied to reduce data size, then bitstream size is reduced, but error vectors are introduced that degrade mesh quality
Solution Approach 1:
The patent converts the harmful quantization errors into useful correction information. By calculating correction vectors that explicitly represent the error between original and reconstructed data, the system transforms the harmful effect of quantization into a correctable signal that improves final reconstruction quality while maintaining compressed bitstream size.
Solution Approach 2:
The patent changes the parameter representation by introducing correction vectors as additional data elements in the bitstream. These vectors modify the reconstruction process by adjusting vertex positions and mesh geometry parameters, effectively changing the reconstruction parameters to compensate for quantization losses without significantly increasing the overall bitstream size.
3Manufacturing precision
If error correction vectors are calculated and transmitted, then reconstruction quality is improved, but bitstream complexity increases
Solution Approach 1:
The patent applies local quality correction by calculating and transmitting correction vectors only for specific mesh elements (patches or vertices) where errors are detected. Rather than correcting the entire mesh uniformly, the system identifies and corrects only the problematic local regions, reducing the overall complexity of the correction data while maintaining reconstruction quality.
Solution Approach 2:
The patent employs partial correction by transmitting correction vectors only when and where needed, rather than applying full correction universally. The system can selectively apply corrections based on error thresholds or mesh regions, reducing the amount of correction data transmitted and processed while maintaining adequate reconstruction quality.
Data Source
AI summary
An apparatus obtains a mesh representation of a 3D object, and performs an encoding process: segmenting the 3D object into 2D projections; encoding the segmented 2D projections into a bitstream; reconstructing a 3D mesh from the segmented and encoded 2D projections; deriving an error vector, describing a shift between 3D data, from patches reconstructed from corresponding encoded patches of the bitstream, and original data in the mesh representation. The patches are submeshes of the reconstructed 3D mesh. The apparatus signals and transmits the error vector in or along with the bitstream. A decoder apparatus receives these and performs a decoding process to form decoded 2D projections of the mesh representation, reconstructs a 3D mesh from decoded 2D projections, applies the patch correction vector elements from the error vector in the decoding process or the reconstructing, produces a modified 3D mesh, as an output mesh and outputs the output mesh.