Cube-Based Projection Mapping for Uniform 360-Degree Sampling
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Solution Overview
Problem
Current methods for processing omnidirectional video frames in virtual reality with head-mounted displays face challenges in achieving uniform sampling rates, leading to degraded encoding and decoding quality due to non-uniform mapping between a sphere and projection faces.
Innovation Solution
A cube-based projection method that applies different mapping functions to various square projection faces, axes, and locations, using conversion circuits to generate pixels for a 360-degree image content, ensuring a more uniform sampling rate through hybrid equi-angular cubemap projections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a uniform mapping function is applied to all square projection faces, then the device complexity is reduced, but the sampling rate uniformity deteriorates
Solution Approach 1:
The patent applies different mapping functions to different square projection faces of the cube-based projection. Specifically, it uses equi-angular mapping for some faces and equirectangular mapping for others, allowing each face to be optimized for its specific geometric characteristics and viewing angle requirements, thereby achieving uniform sampling rates across the entire 360-degree panorama.
2Manufacturing precision
If different mapping functions are applied to different square projection faces, then the sampling rate uniformity is improved, but the device complexity increases
Solution Approach 1:
The patent divides the 360-degree panoramic projection into six separate square faces of a cube, and further segments these faces into different groups that require different mapping functions. This segmentation allows the system to apply equi-angular mapping to faces requiring angular uniformity and equirectangular mapping to faces requiring rectangular distortion correction, optimizing sampling for each segment while managing overall complexity.
3Manufacturing precision
If high resolution omnidirectional video is transmitted, then the image quality is improved, but the bitrate requirement increases
Solution Approach 1:
The patent changes the projection parameters by applying different mapping functions to different cube faces, which optimizes the spatial distribution of pixels and achieves more uniform sampling rates. This parameter optimization reduces redundancy in the encoded video data, allowing high-resolution omnidirectional video to be transmitted at lower bitrates while maintaining image quality.
Data Source
AI summary
A cube-based projection method includes generating pixels of different square projection faces associated with a cube-based projection of a 360-degree image content of a sphere. Pixels of a first square projection face are generated by utilizing a first mapping function set. Pixels of a second square projection face are generated by utilizing a second mapping function set. The different square projection faces include the first square projection face and the second square projection face. The second mapping function set is not identical to the first mapping function set.