Nikon Digital Camera Reference Manual page 121

D
Trimming Movies
Movies must be at least two seconds long. If a copy can not be created
at the current playback position, the current position will be displayed
in red in Step 4 and no copy will be created. The copy will not be saved
if there is insufficient space available on the memory card.
To prevent the camera from turning off unexpectedly, use a fully-
charged battery when editing movies.
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