Video Encoding Syntax Signaling for Cube-Based Projection Packing
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Solution Overview
Problem
Current video encoding methods for 360-degree virtual reality content lack flexibility in packing projection faces, leading to high bitrate requirements and inefficiencies in data compression, especially when the resolution is 4K or higher.
Innovation Solution
A video encoding method that signals syntax elements indicative of packing types for projection faces in a cube-based projection layout, allowing for flexible configuration and efficient data compression by mapping 360-degree content onto projection faces within a bitstream.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed 360 VR projection layout configuration is used, then the encoding process is simplified, but the video encoder loses flexibility for encoding 360-degree image content
Solution Approach 1:
The patent implements dynamic selection of projection face packing types (e.g., cube map, sphere map, equirectangular) through syntax element signaling in the bitstream. The encoder can adaptively choose different packing configurations based on content characteristics, and the decoder parses the signaled syntax elements to apply the corresponding packing type, enabling flexible encoding while maintaining standardized processing.
Solution Approach 2:
The patent introduces syntax elements that signal packing type parameters and projection face arrangement configurations. By changing these parameters dynamically through bitstream signaling, the system can switch between different projection layouts (cube-based, sphere-based, equirectangular) without requiring multiple fixed encoding systems, thus achieving versatility while keeping the encoding process manageable.
2Manufacturing precision
If resolution of omnidirectional video is increased to 4K or higher, then visual quality is improved, but bitrate requirements increase significantly
Solution Approach 1:
The patent segments the omnidirectional video content into multiple projection faces (e.g., six faces for cube map, five faces for sphere map) that can be independently encoded and packed. This segmentation allows for more efficient compression by treating each face as a separate encodable unit, reducing the overall bitrate requirement for 4K or higher resolution omnidirectional video while maintaining visual quality.
Solution Approach 2:
The patent transforms the traditional equirectangular projection into alternative projection layouts such as cube map or sphere map projections. This dimensional transformation reorganizes the 360-degree content into different geometric arrangements that can be more efficiently compressed, thereby reducing bitrate requirements while preserving 4K or higher resolution quality.
3Adaptability or versatility
If multiple packing types for projection faces are supported, then encoding flexibility is improved, but device complexity increases
Solution Approach 1:
The patent designs a universal syntax element signaling mechanism that can indicate multiple packing types (cube map, sphere map, equirectangular) within a single standardized framework. Both encoder and decoder use the same syntax element parsing logic to handle different packing types, achieving multi-functionality without requiring separate processing paths for each packing type, thus limiting the increase in device complexity.
Data Source
AI summary
A video decoding method includes decoding a part of a bitstream to generate a decoded frame, and parsing at least one syntax element from the bitstream. The decoded frame is a projection-based frame that has projection faces packed in a cube-based projection layout. At least a portion of a 360-degree content of a sphere is mapped to the projection faces via cube-based projection. The at least one syntax element is indicative of packing of the projection faces in the cube-based projection layout.