Hierarchical Video Overlay Rendering With Cross-Resolution Glyph Alignment
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Solution Overview
Problem
Hierarchical video coding faces challenges in aligning overlays across different resolutions, leading to misalignment and increased bitrate due to variations in rendering processes such as positioning, hinting, and kerning, which adversely affect visual quality and encoding efficiency.
Innovation Solution
A method for rendering overlays by mapping pixel positions of glyphs across different resolutions using a ratio between resolutions, ensuring alignment and reducing the residual between lower and higher resolutions, thereby encoding the enhancement layer with a smaller bitrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If distinct overlays are rendered directly to both base and enhancement layers, then visual quality is maintained at both resolutions, but alignment precision deteriorates due to rendering variations
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the mapping relationship between pixel positions at different resolutions before rendering overlays. The mapping table is prepared in advance, specifying which pixel positions at the first resolution correspond to which pixel positions at the second resolution. This pre-computed mapping ensures that when overlays are rendered, the glyph positions can be precisely aligned across resolutions by referencing the pre-established mapping, thereby maintaining both alignment precision and visual quality consistency.
2Device complexity
If overlays are scaled from higher resolution, then device complexity is reduced, but manufacturing precision deteriorates due to loss of clarity and sharpness
Solution Approach 1:
The patent applies segmentation by separating the overlay rendering process into distinct segments for different resolutions. Instead of rendering one overlay and scaling it, the system renders separate overlays specifically optimized for the first resolution and the second resolution. The mapping mechanism ensures these segmented renders align perfectly, allowing each resolution to have its own optimized rendering without the quality loss that would result from scaling, while keeping device complexity manageable through the use of a systematic mapping approach.
3Adaptability or versatility
If overlay rendering is performed independently at each resolution, then adaptability is improved, but manufacturing precision deteriorates due to positioning discrepancies
Solution Approach 1:
The patent applies feedback by using the mapping relationship as a feedback mechanism to guide the rendering process at different resolutions. The mapping table provides feedback information about the correspondence between pixel positions, allowing the system to adjust and coordinate the rendering of overlays at the first and second resolutions. This feedback ensures that even though rendering is performed independently at each resolution for adaptability, the glyph positioning remains precisely aligned through the guidance provided by the pre-computed mapping relationships.
Data Source
AI summary
Rendering overlays in a hierarchically encoded video sequence having an enhancement layer and a base layer is embodied in one or more methods, devices, systems and software. A video sequence is represented at a first resolution and a second resolution. A first overlay comprising a first pattern of glyphs is rendered in the video sequence at the first resolution, wherein a first glyph of the one or more glyphs is rendered at a first pixel in the video sequence at the first resolution. A second overlay comprising the first pattern is rendered in the video sequence at the second resolution. The rendering of the second overlay is controlled to render the first glyph at a second pixel position obtained by mapping the first pixel position to the second pixel position according to a ratio between the first resolution and the second resolution.