360-Degree Video Subtitle Positioning via Spherical Coordinates
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Solution Overview
Problem
Current VR systems face challenges in efficiently transmitting and receiving 360-degree video content, particularly in providing robust and flexible data transmission, efficient reproduction, and adaptive subtitle signaling suitable for immersive experiences.
Innovation Solution
The method involves generating and transmitting 360-degree video data, stitching it, projecting onto a 2D image, encoding, and inserting Supplemental Enhancement Information (SEI) messages for subtitle signaling, including subtitle IDs, region IDs, and region information to specify subtitle positions in 360-degree space, which can be fixed or offset based on the viewport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If general TTML based subtitles or bitmap based subtitles are used, then subtitle display is simple, but they are not adapted to 360-degree video and cannot provide immersive subtitle experiences
Solution Approach 1:
The patent changes the parameter representation of subtitle positions from traditional 2D screen coordinates to 3D spherical coordinates (azimuth and elevation angles). This allows subtitles to be positioned in three-dimensional space around the viewer, enabling immersive subtitle experiences that adapt to 360-degree video content while maintaining manageable complexity through standardized parameter sets.
Solution Approach 2:
The patent transitions from 2D subtitle positioning (screen coordinates) to 3D subtitle positioning (spherical coordinates with azimuth and elevation). This dimensional expansion enables subtitles to be placed in three-dimensional space relative to the viewer, providing adaptability to 360-degree video while the structured parameter system keeps the signaling complexity controlled.
2Measurement precision
If 360-degree video data is transmitted with detailed subtitle information, then subtitle positioning accuracy is improved, but data transmission load increases
Solution Approach 1:
The patent uses compact parameter representations for subtitle regions, including minimum/maximum azimuth and elevation angles, and offset values relative to viewport centers. These parameter changes enable precise positioning of subtitles in 3D space while maintaining efficient data encoding that reduces transmission load compared to full coordinate systems.
Solution Approach 2:
The patent transmits only the essential parameters needed for subtitle positioning (azimuth ranges, elevation ranges, offset flags) rather than complete coordinate information for every subtitle element. This partial transmission approach achieves sufficient positioning precision while significantly reducing the data volume that needs to be transmitted.
3Stability of the object's composition
If fixed region information is used for subtitles, then subtitle positioning is stable, but subtitles cannot adapt to changing viewport positions in mobile VR
Solution Approach 1:
The patent introduces dynamic subtitle positioning through offset region information that can be applied relative to the current viewport center. When the offset flag is set, subtitle positions are calculated relative to the viewport rather than fixed in absolute coordinates, allowing subtitles to automatically adapt to changing viewport positions in mobile VR while maintaining stable positioning within each viewport frame.
Solution Approach 2:
The patent creates a universal subtitle positioning system that can operate in multiple modes: fixed region mode for stability when viewport position is constant, and offset region mode for adaptability when viewport position changes. This multi-functional approach allows the same subtitle data to serve both stability and adaptability requirements depending on the playback context.
4Adaptability or versatility
If offset region information is used for subtitles, then subtitle adaptability to viewport changes is improved, but positioning accuracy may vary with different viewport configurations
Solution Approach 1:
The patent uses normalized offset parameters that are calculated relative to the viewport center and scaled according to viewport dimensions. This parameter approach maintains consistent subtitle positioning accuracy across different viewport configurations by adapting the offset calculations to the specific viewport geometry, ensuring that subtitles remain accurately positioned regardless of viewport size or orientation.
Data Source
AI summary
The present invention suggests a method of providing subtitles for a 360 content, the method comprising: generating 360 video data captured by at least one camera; stitching the 360 video data; projecting the 360 video data to a 2D image; encoding the 2D image into a video stream; generating a 360 subtitle Supplemental Enhancement Information (SEI) message for signaling a subtitle for the 360 content; inserting the 360 subtitle SEI message into the video stream; and generating a broadcast signal including the video stream, and transmitting the broadcast signal.