Filter framerate
  Upsamples or downsamples progressive source between specified frame rates.
    Inputs:
       #0: default (video)
    Outputs:
       #0: default (video)
framerate AVOptions:
  fps               <video_rate> ..FV.... required output frames per second rate (default "50")
  interp_start      <int>        ..FV.... point to start linear interpolation (from 0 to 255) (default 15)
  interp_end        <int>        ..FV.... point to end linear interpolation (from 0 to 255) (default 240)
  scene             <double>     ..FV.... scene change level (from 0 to INT_MAX) (default 7)
  flags             <flags>      ..FV.... set flags (default scene_change_detect+scd)
     scene_change_detect              ..FV.... enable scene change detection
     scd                          ..FV.... enable scene change detection


