V-DMC Displacement Coding With Per-Level Lifting Offsets
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Solution Overview
Problem
Existing video-based coding of dynamic meshes (V-DMC) technologies face inefficiencies due to biased transform coefficients, which affect coding efficiency and accuracy, particularly in the lifting transform process.
Innovation Solution
Implement a lifting transform with an offset to adjust transform coefficients to a zero-mean distribution, compensating for bias by determining and applying an offset to the transform coefficients, and signaling this offset in the bitstream for accurate decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a lifting transform is applied to displacement vectors in V-DMC, then transform coefficients are generated for mesh coding, but the transform coefficients exhibit bias (non-zero mean distribution) which reduces coding efficiency and accuracy
Solution Approach 1:
The patent applies an offset to the transform coefficients to change their statistical parameters, specifically adjusting the mean from a non-zero value to zero. This parameter change eliminates the bias in the coefficient distribution, improving both coding efficiency and accuracy simultaneously by centering the coefficient distribution around zero.
Solution Approach 2:
The offset is determined and applied in advance during the encoding process, before quantization and bitstream generation. This preliminary action of bias correction ensures that the transform coefficients are properly centered, which improves subsequent coding steps and overall reconstruction accuracy.
2Device complexity
If transform coefficients with bias are used directly, then the encoding process is simpler, but the reconstruction quality of dynamic meshes deteriorates
Solution Approach 1:
By introducing an offset parameter that adjusts the mean of transform coefficients to zero, the patent improves mesh reconstruction quality without significantly increasing encoding complexity. The offset calculation and application are straightforward operations that maintain process simplicity while enhancing output quality.
3Speed
If no offset is applied to transform coefficients, then the encoding and decoding process is faster, but coding efficiency and accuracy are reduced
Solution Approach 1:
The offset adjustment is a computationally efficient operation that can be performed quickly during encoding and decoding. By changing the parameter (applying offset) rather than redesigning the entire transform process, the patent achieves improved coding efficiency with minimal impact on processing speed.
Data Source
AI summary
Certain aspects of the disclosure provide for encoding and decoding mesh data using a lifting transform. Transform coefficients are determined by applying a lifting transform on displacement vectors representing mesh data. To address systematic bias, such as a non-zero mean distribution, an offset can be determined and applied to transform coefficients per level of detail. An encoder quantizes transform coefficients adjusted by the offset and signals the quantized coefficients and the offset in a bitstream of encoded mesh data. A decoder extracts the quantized transform coefficients and offset per level of detail from the bitstream, inverse quantizes the transform coefficients, applies the offset, and inverse transforms the result to recover displacement vectors and reconstruct the mesh data.