Touch Panel Sample Rate Adaptation for Jitter Reduction
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Solution Overview
Problem
In touch-sensitive devices, the mismatch between touch sampling frequency and screen refresh frequency, along with phase differences, leads to 'jitter' in rendered content due to multiple or stale touch samples during screen refresh cycles.
Innovation Solution
A system and method for sample rate adaptation that adjusts touch panel sampling rates to match screen refresh rates, discarding older samples or averaging them to minimize phase differences, and uses phase adaptation techniques like Kalman filters to reduce phase noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If touch panel sampling frequency exceeds screen refresh frequency, then more touch samples are available for rendering, but multiple touch samples occur during a single VSYNC cycle causing jitter
Solution Approach 1:
The patent applies preliminary action by pre-processing multiple touch samples before rendering. It calculates the average position of multiple touch samples taken during a VSYNC cycle, and uses this averaged position for rendering. This pre-calibration of sample positions eliminates jitter while preserving the benefit of multiple samples.
Solution Approach 2:
The patent merges multiple touch samples by calculating their average position. Instead of using individual touch samples separately, it combines them into a single averaged position that represents the overall touch location during the VSYNC cycle, thereby eliminating jitter caused by using individual samples.
2Speed
If touch sampling frequency is increased, then touch input responsiveness is improved, but phase difference between touch samples and VSYNC signal varies causing jitter
Solution Approach 1:
The patent uses feedback by tracking the phase relationship between touch samples and VSYNC signals over time. It calculates phase differences between consecutive touch samples and adjusts the rendering timing or sample selection based on this feedback, thereby maintaining consistent phase relationship even when sampling frequency varies.
Solution Approach 2:
The patent applies dynamics by making the rendering system adaptive to varying phase differences. Instead of using a fixed sampling strategy, it dynamically adjusts which touch samples to use and when to render them, based on the actual phase relationship between touch sampling and VSYNC signals at each moment.
3Adaptability or versatility
If touch samples are taken at different phases relative to VSYNC, then sampling flexibility is increased, but rendered content exhibits jitter due to non-constant phase difference
Solution Approach 1:
The patent applies preliminary action by pre-calculating the average position of all touch samples taken during a VSYNC cycle before rendering. This pre-processing step ensures that regardless of when individual samples were taken, their averaged position is ready for consistent rendering, eliminating jitter.
Solution Approach 2:
The patent changes the parameter used for rendering from individual touch sample positions to averaged touch sample positions. By transforming multiple varying positions into a single averaged position, it maintains sampling flexibility while achieving rendering stability.
Data Source
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AI summary
A system and method for sample rate adaption of input samples from a touch panel to the screen refresh rate. The system and method provide for touch input information derived from sampling at a first touch input rate to be applied or processed at a second screen refresh rate where the first and second rates differ in frequency and phase. The information is adapted from the first rate to the second rate. Then phase differences including phase introduced as by-product of adapting the frequencies are reduced by phase adaption.