recode all videos in current folder with ffmpeg (decreasing filesize by up to 80%)

convert.rb

# can also be *.flv or *.wmv etc.
files = Dir['*.mp4']

# min size
mb = 10


def size_mb(file)
  (File.size(file).to_f / 1024 / 1024).round
end

# only select files that have no encoded version and are larger than `mb` 
large = files.reject{|i| files.include?( "encoded_#{i}" ) }.reject{|i| i['encoded']}.select{|i| size_mb(i) > mb }

count = large.count
large.each_with_index do |file, i|
  puts "[#{Time.now.to_s}] Converting #{file} (#{i+1}/#{count})..."
  f = Shellwords.escape(file)
  
  # preset veryfast, ca. 1:1 time encoding on MacAir and small files
  # level 4 + profile main: most devices
  # crf 25  -> Quality level, 0 -> Best, 23 -> default
  # map_matadata -> Copy meta tags over
  system "ffmpeg -i #{f} -preset veryfast -c:v libx264 -profile:v main -level 4 -c:a libfaac -q:a 100 -crf 25 -map_metadata 0 encoded_#{f} 2>/dev/null"
  puts "[#{Time.now.to_s}] Before: #{size_mb(file)}mb;   After: #{size_mb("encoded_#{file}")}mb"
end