Plesiochronous Camera Synchronization via Reverse Channel Feedback
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Solution Overview
Problem
In applications requiring synchronization of multiple cameras, such as surround view in automotive vehicles, dynamic skew due to variations in data transmission mediums, camera and receiver variations, and clock frequency deviations leads to synchronization challenges, resulting in high memory requirements for video buffering and potential frame misalignment.
Innovation Solution
A multiple camera synchronization system that enables plesiochronous operation by generating synchronization data based on data packets and modulating it into a reverse channel, allowing simultaneous transmission with forward channel data, thereby minimizing skew and enabling low skew synchronization across multiple cameras.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple cameras operate independently with separate data transmission, then each camera can function autonomously, but synchronization between cameras deteriorates due to dynamic skew from transmission medium variations, camera variations, and clock frequency deviations
Solution Approach 1:
The receiver measures the arrival time of data packets from multiple cameras and generates synchronization data based on these measurements. This synchronization data is then modulated and transmitted back to the cameras in the reverse channel, creating a feedback loop that enables continuous synchronization adjustment and compensates for dynamic skew variations
Solution Approach 2:
The system performs preliminary synchronization by measuring packet arrival times and generating synchronization data before video frame misalignment occurs. This preliminary action prevents the need for extensive buffering memory by aligning camera operations in advance
2Reliability
If synchronization data is transmitted separately from video data, then synchronization information can be clearly communicated, but transmission efficiency deteriorates due to requiring additional dedicated communication channels
Solution Approach 1:
The system merges the forward channel for video data transmission with the reverse channel for synchronization data transmission into a single bidirectional communication link. This allows simultaneous transmission of both video data and synchronization data over the same physical medium, improving transmission efficiency while maintaining reliability
Solution Approach 2:
The communication link is designed to serve multiple functions: transmitting high-speed video data in the forward direction and transmitting low-speed synchronization control data in the reverse direction. This multi-functionality eliminates the need for separate dedicated channels for each type of data
Data Source
AI summary
A system for at least substantially plesiochronously operating a receiver in communication with a plurality of cameras (e.g., at least two plesiochronously operational cameras) is described. In one or more implementations, the system includes a plurality of cameras. Each camera is configured to generate a signal for transmission via a communications link, and the signal comprises data packets encoded in a forward channel. The system also includes a receiver communicatively coupled to the plurality of cameras via the single-ended communications link. The receiver is configured to generate a synchronization data based upon at least one of the data packets. The receiver is also configured to modulate the signal to encode the synchronization data in a reverse channel so that the signal comprises the forward channel data and the reverse channel data simultaneously.