API implemetation of ffmpeg callback with workers and async.
This is the line we need to use to export ... reasonable:
ffmpeg -ss 2 -i Export\ Buttons-2019-10-15_14.56.53.mkv -filter_complex "[0:v] fps=8,scale=1024:-1,split [a][b];[a] palettegen [p];[b][p] paletteuse" ExportButton.gif