Configurable Tear Thresholds for Low Latency VR Display
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Solution Overview
Problem
In virtual reality (VR) and gaming devices, turning on vertical synchronization (V-SYNC) reduces latency but can cause undesirable image tearing when new images are not ready in time, leading to a less than desirable user experience due to the need to re-present prior images.
Innovation Solution
Implementing a system that allows for configurable tear thresholds to define conditions under which tearing is acceptable, enabling the presentation of the most up-to-date image information by determining whether rendered frames are received before specific timing events, and communicating them to the display device accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If V-SYNC is turned on to reduce latency, then image latency is reduced, but image tearing occurs when new images are not ready in time
Solution Approach 1:
The system dynamically adjusts the V-SYNC behavior based on frame readiness timing. When a new frame is ready before the V-SYNC deadline, it is presented immediately without tearing. When a frame is not ready by the deadline, the system allows tearing to occur rather than waiting for the next frame, thus avoiding the latency penalty of re-presenting old frames. This dynamic decision-making resolves the contradiction between latency reduction and tearing prevention.
Solution Approach 2:
The patent changes the timing parameter of frame presentation from a fixed V-SYNC schedule to a flexible timing mechanism. By monitoring when frames are actually ready and adjusting the presentation timing accordingly, the system can present frames as soon as they are rendered without being constrained by fixed vertical synchronization intervals, thereby reducing latency while accepting tearing only when necessary.
2Loss of time
If V-SYNC is turned off to present new images immediately, then image latency is minimized, but image tearing occurs when the display is in the middle of presenting a prior image
Solution Approach 1:
The system implements dynamic frame presentation timing that adapts to frame readiness. Instead of strictly following V-SYNC intervals or completely disabling synchronization, the system presents frames as soon as they are ready, using dynamic timing decisions that balance between immediate presentation (low latency) and waiting for appropriate display timing (tear avoidance).
Solution Approach 2:
The system performs preliminary timing analysis to determine the optimal presentation moment for each frame. By evaluating when the frame is ready relative to the display scan position, the system can make informed decisions about whether to present immediately or wait, thus preliminarily preparing the timing strategy before actual frame presentation occurs.
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AI summary
Methods and devices for presenting a virtual reality image may include rendering at least one image frame received from an application for a virtual reality image for display on a display device. The methods and devices may include receiving a selection of one of a plurality of tear thresholds that define conditions for tearing in a displayed image. The methods and devices may include determining whether the rendered frame is received prior to the selected one of the plurality of tear thresholds, wherein the selected one of the plurality of tear thresholds occurs after a frame timing event that corresponds to a deadline for initiating display of a new frame. The methods and device may include communicating the rendered image frame to the display device for presentation on the display device when the rendered frame is received prior to the selected one of the plurality of tear thresholds.