Variable Display Refresh Rate Synchronization
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Solution Overview
Problem
Electronic device displays face issues with visual corruption and discontinuities due to mismatched refresh rates and frame rates, leading to desynchronization, tearing, and jank, especially when variable frame rate content is forced into unintended cadences.
Innovation Solution
Implementing variable refresh rate (VRR) technology that synchronizes display refresh rates with content generation and presentation devices, using a TE signal to manage refresh cycles and emission pulses, allowing for dynamic adjustment of refresh rates based on hardware and software properties to reduce latency and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the display uses a fixed refresh rate, then the display timing is simple and stable, but visual corruption and discontinuities occur when content frame rate does not match the refresh rate
Solution Approach 1:
The display refresh rate is made dynamic rather than fixed. The system adjusts the refresh rate based on the content frame rate, allowing the display to adapt to different content types (video, animation, static images) and eliminate visual corruption while maintaining reliability.
Solution Approach 2:
The refresh rate parameter is changed dynamically based on content requirements. By monitoring the content frame rate and adjusting the refresh rate parameter accordingly, the system achieves better visual quality without requiring complex additional hardware.
2Reliability
If the display refresh rate is increased to match high frame rate content, then visual quality improves, but power consumption increases
Solution Approach 1:
The refresh rate is dynamically adjusted based on content requirements rather than maintaining a constant high rate. This allows the display to consume less power when high refresh rates are not needed, while still achieving high visual quality when presenting high frame rate content.
Solution Approach 2:
The system uses periodic TE signals to control when refresh cycles occur. By spacing refresh cycles appropriately based on content frame rate, the system achieves smooth visual presentation while avoiding unnecessary power consumption from excessive refresh operations.
3Reliability
If the display waits for content to be ready before refreshing, then visual synchronization improves, but latency increases
Solution Approach 1:
The content generation device prepares visual content in advance and sends it to the content presentation device before it is needed for display. This preliminary action allows the display to refresh without waiting, reducing latency while maintaining synchronization through the VRR mechanism.
Solution Approach 2:
The TE signal provides feedback between the content presentation device and content generation device, allowing the system to coordinate content delivery with display refresh cycles. This feedback mechanism enables the system to achieve visual synchronization without excessive latency by optimizing the timing of content transmission.
4Device complexity
If the display forces variable frame rate content into a fixed cadence, then display timing remains simple, but tearing and jank occur
Solution Approach 1:
Instead of forcing variable frame rate content into a fixed cadence, the display timing is made dynamic to match the content frame rate. This eliminates tearing and jank while not significantly increasing complexity, as the system uses the existing TE signal mechanism to achieve this adaptation.
Data Source
AI summary
Methods, systems, and apparatus, including computer programs encoded on computer storage media, for enabling a variable refresh rate on a display. One of the methods includes receiving, from a content presentation device, a first signal set to a first value; completing generation of first visual content; and after completing the generation of the first visual content, determining that the first signal is set to the first value and a second threshold duration of time has not expired; sending, to the content presentation device, the first visual content, wherein sending the first visual content causes the content presentation device to change the first signal from the first value to the second value; and after sending the first visual content, receiving, from the content presentation device, the first signal set to the second value.