-r[:stream_specifier] fps (input/output,per-stream)
           Set frame rate (Hz value, fraction or abbreviation).

           As an input option, ignore any timestamps stored in the file and instead
           generate timestamps assuming constant frame rate fps.  This is not the
           same as the -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 -framerate instead of the input option -r.

           As an output option, duplicate or drop input frames to achieve constant
           output frame rate fps.





-framerate
           Set the grabbing frame rate. Default is "ntsc", corresponding to a frame
           rate of "30000/1001".