Filter colorkey
  Turns a certain color into transparency. Operates on RGB colors.
    slice threading supported
    Inputs:
       #0: default (video)
    Outputs:
       #0: default (video)
colorkey AVOptions:
  color             <color>      ..FV..... set the colorkey key color (default "black")
  similarity        <float>      ..FV..... set the colorkey similarity value (from 0.01 to 1) (default 0.01)
  blend             <float>      ..FV..... set the colorkey key blend value (from 0 to 1) (default 0)

This filter has support for timeline through the 'enable' option.

