Type Alias FrameGrab 

pub type FrameGrab = Arc<dyn Fn() -> Result<Vec<u8>, String> + Send + Sync>;

Grab a single JPEG frame (blocking). Resolved from a camera id at start time and held for the run’s duration, so later /api/camera/config edits can’t repoint a running capture.

Aliased Type

pub struct FrameGrab { /* private fields */ }