Rolling Shutter Compensation for Signal Delay Measurement
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Solution Overview
Problem
Rolling shutter mechanisms in cameras introduce errors in signal delay measurement by capturing image frames at different times, making it complex to determine the relative timing of audio and video signals.
Innovation Solution
A method for rolling shutter compensation involves receiving a video signal with a video test pattern, displaying it, capturing the video, monitoring multiple regions, detecting the temporal event times in each region, and extrapolating these times to calculate the time the event would appear at a selected region, assuming an update direction for the camera.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a rolling shutter mechanism is used to capture video frames, then the camera can record video continuously with lower complexity, but the measurement precision of signal delay deteriorates due to capturing different parts of the frame at different times
Solution Approach 1:
The video frame is divided into multiple regions (e.g., top region, bottom region) and the temporal event is detected independently in each region. This segmentation allows the system to capture timing information from different parts of the rolling shutter scan and reconstruct the true temporal relationship between audio and video signals by compensating for the sequential capture nature of rolling shutter.
Solution Approach 2:
A computational compensation mechanism is introduced as an intermediary between the rolling shutter capture process and the delay measurement. This intermediary calculates the expected position of the temporal event in each monitored region based on the rolling shutter scan direction and timing, then uses this information to correct the measured delays, effectively mediating the distortion caused by rolling shutter.
2Reliability
If multiple regions of the display are monitored to detect temporal events, then the measurement reliability improves through multiple data points, but the device complexity increases due to the need to monitor and process multiple regions
Solution Approach 1:
The display area is segmented into multiple monitoring regions, each independently tracking the temporal event. This segmentation provides multiple independent measurements of the same event, increasing reliability through redundancy. The processing complexity is managed by focusing detection only in these specific regions rather than analyzing the entire frame.
Solution Approach 2:
The system uses the known rolling shutter scan direction and timing as feedback to predict where the temporal event should appear in each monitored region. This feedback mechanism allows the system to adjust its expectations and measurements based on the camera's capture characteristics, improving reliability while keeping processing manageable through pattern recognition.
Data Source
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AI summary
A method for rolling shutter compensation during signal delay measurement, comprising displaying a video test pattern on a display, said video test pattern having a temporal event; capturing a video of the display, by a camera; monitoring a plurality of regions of the display in the video; detecting times (1230, 1240) at which the temporal event appears in each monitored region of the display in the video; and extrapolating the detected times (1230, 1240) to calculate the time (1250) at which said temporal event would appear at a selected region of the video.