Filter lenscorrection
  Rectify the image by correcting for lens distortion.
    slice threading supported
    Inputs:
       #0: default (video)
    Outputs:
       #0: default (video)
lenscorrection AVOptions:
  cx                <double>     ..FV.... set relative center x (from 0 to 1) (default 0.5)
  cy                <double>     ..FV.... set relative center y (from 0 to 1) (default 0.5)
  k1                <double>     ..FV.... set quadratic distortion factor (from -1 to 1) (default 0)
  k2                <double>     ..FV.... set double quadratic distortion factor (from -1 to 1) (default 0)


