Why clips start before the motion

The last few seconds are always buffered, so you see the approach.

OdinCam continuously keeps the most recent few seconds of video in memory. When something triggers, that buffer goes into the file first.

This matters more than it sounds. Without it, a clip begins at the moment the detector was already sure — by which point somebody is standing in the middle of frame and you've missed them walking in.

The cost is that video is being compressed the entire time monitoring is active, not only while recording. That's the main reason OdinCam uses some CPU even when nothing is happening.

Clips start at the nearest keyframe, so occasionally you'll get slightly more lead-in than you asked for.