Filter ssim
  Calculate the SSIM between two video streams.
    Inputs:
       #0: main (video)
       #1: reference (video)
    Outputs:
       #0: default (video)
ssim AVOptions:
  stats_file        <string>     ..FV..... Set file where to store per-frame difference information
  f                 <string>     ..FV..... Set file where to store per-frame difference information

framesync AVOptions:
  eof_action        <int>        ..FV..... Action to take when encountering EOF from secondary input  (from 0 to 2) (default repeat)
     repeat          0            ..FV..... Repeat the previous frame.
     endall          1            ..FV..... End both streams.
     pass            2            ..FV..... Pass through the main input.
  shortest          <boolean>    ..FV..... force termination when the shortest input terminates (default false)
  repeatlast        <boolean>    ..FV..... extend last frame of secondary streams beyond EOF (default true)


