Use qt-faststart to move the moov atom on all mp4 files in a given folder

faststart_dir.rb

#!/usr/bin/env ruby

require 'fileutils'

QT_FASTSTART='/usr/local/bin/qt-faststart'

if ARGV.count != 1
  puts "Usage: #{__FILE__} folder"
  exit 1
end

base_dir = File.realdirpath ARGV[0]

unless Dir.exists?  base_dir
  puts "#{ARGV[0]} is not a directory. Existing"
  exit 1
end

Dir[base_dir + File::Separator + '**' + File::Separator + '*.mp4'].each do |f| 
  cmd = "#{QT_FASTSTART} \"#{f}\" \"#{f}.tmp\""
  puts cmd
  begin
    puts `#{cmd}`
    FileUtils.mv("#{f}.tmp", f)  if $?.exitstatus == 0 && (File.exists? "#{f}.tmp")
  rescue  StandardError => e
    puts "Something went wrong processing #{f} : #{e}"
  end
end