Filter readvitc
  Read vertical interval timecode and write it to frame metadata.
    Inputs:
       #0: default (video)
    Outputs:
       #0: default (video)
readvitc AVOptions:
  scan_max          <int>        ..FV..... maximum line numbers to scan for VITC data (from -1 to INT_MAX) (default 45)
  thr_b             <double>     ..FV..... black color threshold (from 0 to 1) (default 0.2)
  thr_w             <double>     ..FV..... white color threshold (from 0 to 1) (default 0.6)


