Filter hqx
  Scale the input by 2, 3 or 4 using the hq*x magnification algorithm.
    slice threading supported
    Inputs:
       #0: default (video)
    Outputs:
       #0: default (video)
hqx AVOptions:
  n                 <int>        ..FV..... set scale factor (from 2 to 4) (default 3)


