Dynamic Multi-Display Refresh Through Timestamp Feedback
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Solution Overview
Problem
Large video displays with multiple displays experience display refresh rate drift due to phase-locked loop-induced frequency drift, leading to unsynchronized refresh rates and artifacts like tearing or blanking, which existing synchronization methods like Adaptive-Sync and network protocols fail to address across multiple computing systems.
Innovation Solution
A control computing system periodically requests display refresh timestamps from individual display systems, adjusting the clock of out-of-sync systems via phase-locked loop control registers to maintain synchronized refresh rates across multiple displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If network synchronization protocols (NTP, PTP) are used to synchronize computing systems, then time synchronization is improved, but display refresh rate synchronization deteriorates due to phase-locked loop-induced frequency drift
Solution Approach 1:
The system implements a feedback mechanism where the control computing system periodically requests display refresh timestamps from individual display systems, compares them against a reference timestamp, and sends clock adjustment information back to out-of-sync systems. This closed-loop feedback continuously corrects phase-locked loop-induced frequency drift and maintains synchronized display refresh rates across all displays in the multi-display system.
2Reliability
If Adaptive-Sync is used to match display refresh rate to GPU rendering rate, then display synchronization is improved, but it only works for single display and cannot support multiple computing systems
Solution Approach 1:
The control computing system implements a universal synchronization mechanism that can manage multiple display systems simultaneously. By maintaining a reference display refresh timestamp and periodically querying timestamps from all display systems, the system provides synchronized refresh rate control across multiple displays and computing systems, extending the functionality beyond single-display Adaptive-Sync to multi-display environments.
3Reliability
If display refresh rate is increased to improve viewing quality, then display quality is improved, but phase-locked loop-induced frequency drift increases leading to more severe synchronization errors
Solution Approach 1:
The system implements a feedback mechanism where the control computing system periodically requests display refresh timestamps from individual display systems, compares them against a reference timestamp, and sends clock adjustment information back to out-of-sync systems. This closed-loop feedback continuously corrects phase-locked loop-induced frequency drift and maintains synchronized display refresh rates across all displays in the multi-display system.
Data Source
AI summary
In multi-display systems, such as video walls, comprising a control computing system providing content to multiple display computing systems driving a plurality of displays, the refresh rates of the displays can drift over time. This drift can introduce display artifacts, which can make for an unpleasant viewing experience. To counteract display refresh drift, a control system periodically compares display refresh timestamps of the individual display systems to a reference display refresh timestamp of a reference display system. If the difference exceeds a threshold, the control system determines clock adjustment information that is sent to the display system exhibiting drift. The display system utilizes the clock adjustment information to adjust the frequency of a display system clock, which can be done by writing the clock adjustment information to registers that control the behavior of a phase-locked loop that generates the clock used by display refresh circuitry.