As an input option, ignore any timestamps stored in the file and instead
generate timestamps assuming constant frame rate @var{fps}.
+This is not the same as the @option{-framerate} option used for some input formats
+like image2 or v4l2 (it used to be the same in older versions of FFmpeg).
+If in doubt use @option{-framerate} instead of the input option @option{-r}.
As an output option, duplicate or drop input frames to achieve constant output
frame rate @var{fps}.