Filter blackdetect
  Detect video intervals that are (almost) black.
    Inputs:
       #0: default (video)
    Outputs:
       #0: default (video)
blackdetect AVOptions:
  d                 <double>     ..FV..... set minimum detected black duration in seconds (from 0 to DBL_MAX) (default 2)
  black_min_duration <double>     ..FV..... set minimum detected black duration in seconds (from 0 to DBL_MAX) (default 2)
  picture_black_ratio_th <double>     ..FV..... set the picture black ratio threshold (from 0 to 1) (default 0.98)
  pic_th            <double>     ..FV..... set the picture black ratio threshold (from 0 to 1) (default 0.98)
  pixel_black_th    <double>     ..FV..... set the pixel black threshold (from 0 to 1) (default 0.1)
  pix_th            <double>     ..FV..... set the pixel black threshold (from 0 to 1) (default 0.1)


