Filter drawgrid
  Draw a colored grid on the input video.
    Inputs:
       #0: default (video)
    Outputs:
       #0: default (video)
drawgrid AVOptions:
  x                 <string>     ..FV..... set horizontal offset (default "0")
  y                 <string>     ..FV..... set vertical offset (default "0")
  width             <string>     ..FV..... set width of grid cell (default "0")
  w                 <string>     ..FV..... set width of grid cell (default "0")
  height            <string>     ..FV..... set height of grid cell (default "0")
  h                 <string>     ..FV..... set height of grid cell (default "0")
  color             <string>     ..FV..... set color of the grid (default "black")
  c                 <string>     ..FV..... set color of the grid (default "black")
  thickness         <string>     ..FV..... set grid line thickness (default "1")
  t                 <string>     ..FV..... set grid line thickness (default "1")
  replace           <boolean>    ..FV..... replace color & alpha (default false)

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

