@var{force_key_frames} may not be set accurately because of rounding
issues, with the consequence that a key frame time may result set just
before the specified time. For constant frame rate videos a value of
-1/2*@var{frame_rate} should address the worst case mismatch between
+1/(2*@var{frame_rate}) should address the worst case mismatch between
the specified time and the time set by @var{force_key_frames}.
@item segment_times @var{times}