FFMpeg multi video overlay

ffmpeg_merge.thor

class Ffmpeg < Thor
  package_name "ffmpeg"

  desc "install", "install ffmpeg"
  def install
    `brew install ffmpeg`
  end

  desc "merge FILE1 FILE2 FILE3 FILE4 OUTPUT", ""
  def merge(file_1, file_2, file_3, file_4, output_file)
    result_height = 360*2
    result_width  = 640*2


    individual_height = result_height / 2
    individual_width  = result_width  / 2

    overlay_options="shortest=1" #Shortest video should determine the length of the video

    cmd = "ffmpeg -i #{file_1} -i #{file_2} -i #{file_3} -i #{file_4} -filter_complex \"nullsrc=size=#{result_width}x#{result_height} [base]; [0:v] setpts=PTS-STARTPTS, scale=#{individual_width}x#{individual_height} [upperleft]; [1:v] setpts=PTS-STARTPTS, scale=#{individual_width}x#{individual_height} [upperright]; [2:v] setpts=PTS-STARTPTS, scale=#{individual_width}x#{individual_height} [lowerleft]; [3:v] setpts=PTS-STARTPTS, scale=#{individual_width}x#{individual_height} [lowerright]; [base][upperleft] overlay=#{overlay_options} [tmp1]; [tmp1][upperright] overlay=#{overlay_options}:x=#{individual_width} [tmp2]; [tmp2][lowerleft] overlay=#{overlay_options}:y=#{individual_height} [tmp3]; [tmp3][lowerright] overlay=#{overlay_options}:x=#{individual_width}:y=#{individual_height}\" -c:v libx264 #{output_file}"

    `#{cmd}`
  end
end

https://trac.ffmpeg.org/wiki/Create%20a%20mosaic%20out%20of%20several%20input%20videos was super great!

https://www.ffmpeg.org/ffmpeg-filters.html#Examples-50