There is normal space and supercruise. Supercruise is for high speed travel between normal space locations. Not fast travel. In normal you can do whatever you want like flying into space stations, PvP/PvE engagement, mining, collecting space stuff, chilling, repairing,...

Usually before combat, in supercruise, 1 person has to interdict another, a mini game on both sides. This could be the indicator to start recording. Now in normal space, there will be combat happening. The Death screen could be the stop recording indicator. Same as the jump to supercruise with its animated loading screen after winning a fight. For combat there is a wide range of time. Sometimes couple of seconds or half an hour. Depending on skill differences, ship builds or one running and more.

Atm I start/stop the recording manually. Just an idea for convenience.