Filter fade
  Fade in/out input video.
    slice threading supported
    Inputs:
       #0: default (video)
    Outputs:
       #0: default (video)
fade AVOptions:
  type              <int>        ..FV....... set the fade direction (from 0 to 1) (default in)
     in              0            ..FV....... fade-in
     out             1            ..FV....... fade-out
  t                 <int>        ..FV....... set the fade direction (from 0 to 1) (default in)
     in              0            ..FV....... fade-in
     out             1            ..FV....... fade-out
  start_frame       <int>        ..FV....... Number of the first frame to which to apply the effect. (from 0 to INT_MAX) (default 0)
  s                 <int>        ..FV....... Number of the first frame to which to apply the effect. (from 0 to INT_MAX) (default 0)
  nb_frames         <int>        ..FV....... Number of frames to which the effect should be applied. (from 1 to INT_MAX) (default 25)
  n                 <int>        ..FV....... Number of frames to which the effect should be applied. (from 1 to INT_MAX) (default 25)
  alpha             <boolean>    ..FV....... fade alpha if it is available on the input (default false)
  start_time        <duration>   ..FV....... Number of seconds of the beginning of the effect. (default 0)
  st                <duration>   ..FV....... Number of seconds of the beginning of the effect. (default 0)
  duration          <duration>   ..FV....... Duration of the effect in seconds. (default 0)
  d                 <duration>   ..FV....... Duration of the effect in seconds. (default 0)
  color             <color>      ..FV....... set color (default "black")
  c                 <color>      ..FV....... set color (default "black")

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

