ffmpeg.rb

#!/usr/bin/env ruby

class FFMPEG
  def self.generate_filter
    scale_segment = ''
    ingredients.each_with_index do |_, i|
      scale_segment += "[#{i}:v]scale=1920:1080:force_original_aspect_ratio=1[v#{i}];"
    end

    output_segment = ''
    ingredients.each_with_index do |_, i|
      output_segment += "[v#{i}][#{i}:a]"
    end
    output_segment += "concat=n=#{ingredients.length}:v=1:a=1[v][a]"

    "-filter_complex \"#{scale_segment} #{output_segment}\" -map \"[v]\" -map \"[a]\""
  end

  def self.ingredients
    Dir.entries('media').select { |f| File.file?(File.join('media', f)) && f.include?('mp4') }.map { |f| "media/#{f}" }
  end

  def self.inputs
    ingredients.map { |path| "-i #{path}" }.join(' ')
  end

  def self.invocation
    "ffmpeg #{inputs} -c:v h264_videotoolbox -vsync 2 -b:v 8000k #{generate_filter} stitched-video.mp4"
  end
end

puts FFMPEG.invocation