Filter signature
  Calculate the MPEG-7 video signature
    Inputs:
        dynamic (depending on the options)
    Outputs:
       #0: default (video)
signature AVOptions:
  detectmode        <int>        ..FV..... set the detectmode (from 0 to 2) (default off)
     off             0            ..FV.....
     full            1            ..FV.....
     fast            2            ..FV.....
  nb_inputs         <int>        ..FV..... number of inputs (from 1 to INT_MAX) (default 1)
  filename          <string>     ..FV..... filename for output files (default "")
  format            <int>        ..FV..... set output format (from 0 to 1) (default binary)
     binary          0            ..FV.....
     xml             1            ..FV.....
  th_d              <int>        ..FV..... threshold to detect one word as similar (from 1 to INT_MAX) (default 9000)
  th_dc             <int>        ..FV..... threshold to detect all words as similar (from 1 to INT_MAX) (default 60000)
  th_xh             <int>        ..FV..... threshold to detect frames as similar (from 1 to INT_MAX) (default 116)
  th_di             <int>        ..FV..... minimum length of matching sequence in frames (from 0 to INT_MAX) (default 0)
  th_it             <double>     ..FV..... threshold for relation of good to all frames (from 0 to 1) (default 0.5)


