Segmented Sphere Projection Layout for 360 Video Encoding
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Solution Overview
Problem
Existing methods for encoding 360-degree omnidirectional image/video content in VR projection layouts face inefficiencies due to non-compact layouts and image content discontinuity edges, leading to poor coding efficiency and image quality after compression.
Innovation Solution
The proposed solution involves generating and encoding projection-based frames using a segmented sphere projection (SSP) layout, which includes mapping a sphere's north and south polar regions onto circular faces and non-polar ring-shaped segments onto rectangular faces, with the use of guard bands and padding to reduce artifacts and improve image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional 360 VR projection layout is used, then the omnidirectional content can be represented, but the layout is not compact and has many image content discontinuity edges, leading to poor coding efficiency
Solution Approach 1:
The patent divides the sphere into multiple segments (polar regions and non-polar ring-shaped segments) and maps them to different projection faces (circular and rectangular). This segmentation allows for a more compact arrangement of projection faces, reducing the overall layout area while maintaining complete 360-degree coverage and minimizing discontinuity edges.
2Reliability
If traditional 360 VR projection layout is used, then the omnidirectional content can be represented, but there are many image content discontinuity edges, leading to poor image quality after compression
Solution Approach 1:
By segmenting the sphere into polar and non-polar regions with different projection mappings, the patent reduces the number of discontinuity edges in the final projection layout. The circular projection faces for polar regions and rectangular faces for non-polar regions are arranged to minimize edge artifacts, improving image quality after compression.
Solution Approach 2:
The patent introduces guard bands as intermediary elements between adjacent projection faces. These guard bands act as buffers that prevent discontinuity edges from creating harmful artifacts during compression, thereby improving image quality by isolating potential discontinuities.
3Reliability
If guard bands and padding are employed in SSP layout, then image quality after compression is improved, but the device complexity increases
Solution Approach 1:
The patent applies guard bands and padding during the projection frame generation stage, before the actual video encoding process. This preliminary action prepares the image data in advance, reducing artifacts that would otherwise require complex post-processing during compression, thereby improving image quality without significantly increasing overall system complexity.
Data Source
AI summary
A video processing method includes receiving an omnidirectional content corresponding to a sphere, generating a projection-based frame according to at least the omnidirectional content and a segmented sphere projection (SSP) format, and encoding, by a video encoder, the projection-based frame to generate a part of a bitstream. The projection-based frame has a 360-degree content represented by a first circular projection face, a second circular projection face, and at least one rectangular projection face packed in an SSP layout. A north polar region of the sphere is mapped onto the first circular projection face. A south polar region of the sphere is mapped onto the second circular projection face. At least one non-polar ring-shaped segment between the north polar region and the south polar region of the sphere is mapped onto said at least one rectangular projection face.