Variable Refresh Rate Display Frame Reinsertion
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Solution Overview
Problem
Displays with variable refresh rates face issues such as frame delay and image flickering due to discrepancies in refresh rates, leading to increased input lag and undesirable image discrepancies, particularly when new frames are rendered at rates outside the supported refresh range.
Innovation Solution
The method involves varying the display's refresh rate by re-providing the current frame for display prior to presenting a new frame, adjusting the vertical blanking period to ensure new frames are displayed as soon as they are rendered, and determining safe rate ranges within the display's supported refresh rate to avoid flickering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the display is refreshed at a rate faster than the maximum supported refresh rate to reduce frame delay, then input lag is reduced, but image tearing occurs
Solution Approach 1:
The patent implements dynamic refresh rate adjustment by monitoring the render rate and adapting the display refresh rate accordingly. When the render rate exceeds the maximum supported refresh rate, the system dynamically selects alternative strategies such as frame reinsertion or skipping to maintain display stability while minimizing input lag. This dynamic adaptation resolves the contradiction by allowing the system to operate at different points on the performance spectrum depending on real-time conditions.
Solution Approach 2:
The patent changes the refresh rate parameter based on the render rate to optimize both frame delay and image quality. By adjusting the refresh rate parameter dynamically - lowering it when necessary to prevent tearing or using frame reinsertion techniques - the system maintains reliable image display while minimizing time loss. This parameter change strategy directly addresses the technical contradiction between speed and reliability.
2Reliability
If the display is refreshed at a rate slower than the minimum supported refresh rate to prevent image tearing, then image quality is maintained, but input lag increases
Solution Approach 1:
The patent applies preliminary action by reinserting frames earlier than they would naturally be displayed. When a frame is rendered, the system can hold it in a buffer and present it at the next appropriate refresh opportunity, ensuring that the display shows the most recent available frame without exceeding the maximum refresh rate. This preliminary preparation of frame data reduces the effective input lag while maintaining image quality.
Solution Approach 2:
The patent introduces an intermediary frame buffer between the renderer and display that mediates the rate mismatch. This buffer allows the system to decouple the render rate from the display refresh rate, enabling the display to operate within its supported range while still reflecting recent frame data. The intermediary buffer resolves the contradiction by absorbing the timing differences without losing frame data or causing tearing.
3Loss of time
If the refresh rate is varied frequently to adapt to render rate changes, then frame delay is reduced, but display flickering occurs
Solution Approach 1:
The patent applies partial action by making selective adjustments to the refresh rate rather than continuously varying it. The system monitors render rate changes and only adjusts the refresh rate when necessary to prevent frame delay, maintaining a stable refresh rate during normal operation. This selective adjustment approach reduces frame delay when needed while avoiding the flickering that results from frequent refresh rate changes.
Solution Approach 2:
The patent implements feedback control by continuously monitoring the render rate and adjusting the refresh rate based on the difference between the two rates. The feedback mechanism includes thresholds and hysteresis to prevent oscillation, ensuring that refresh rate changes are made only when necessary and in a controlled manner. This feedback approach resolves the contradiction by adapting to render rate changes while maintaining display stability.
Data Source
AI summary
Briefly, methods and apparatus provide image content to, and display image content on, displays with a variable refresh rate that reduce frame delays and avoid display image flickering problems. In one example, the methods and apparatus are operative to vary a display's refresh rate by varying a current frame's vertical blanking period by re-providing the current frame for display prior to providing a new frame for display. In this fashion, the displaying of a new frame may be advanced by assuring that a new frame can be provided for display as soon as it has been rendered and available for display. In addition, by re-providing the current frame for display prior to providing a new frame for display, new frames may be provided for display at rates within a safe rate range such that display image flickering issues are avoided or reduced.