Communicating between the dash cam and the central server will be challenging, as we need to determine how they communicate and how the dash cam locates and uploads images. Since we’re no longer building a web app, Andy can focus more on integration, and we plan to implement this in blocks to manage complexity and reduce risks.
Determining how images and metadata are stored on the dash cam is an issue we talked about and need more discussion on tradeoffs. We discussed storing the information about the license plate number that we sent on dash cams so we do not send them again in recent times. The benefit of this would be to reduce flushing to end users, but this introduces more computational complexity on Raspberry Pi and might cause unconfident images only being sent once that are not enough for human verification. We also need more discussion on if we should store temporary images on RAM and send them to the server directly, or we should always store them to SD card first and send from SD card.
Changes
Based on feedback from our design report, we decided to switch to an API-first approach instead of a full web app, as it better aligns with our system’s intended use. Since law enforcement agencies likely already have their own software, exposing an API enables seamless integration rather than requiring them to adopt a separate interface. Moving forward, we plan to expose a single POST endpoint for adding plates to the watchlist. To ensure security, external services will be required to use an API key to access the endpoint, and we will implement audit logging to track who added what. If a match is detected, we will log the event as if notifying a tip line—without actually sending notifications. This keeps the system lightweight and secure while still preserving important tracking data.
Based on dash cam bringup experimentations, we found writing raw footage to SD card to be the performance bottleneck, limiting the frames per second the dash cam can capture. To address this issue, we decided to store raw footage at 480p, while still having the dash cam inference on higher resolution (2304*1296) frames.
