initial_sketch.rb

require "rubygems"
require "ffmpeg"

include FFMpeg

PRESETS = {
  :mp4_240x180_400k_aac => {
    :block => lambda {
      resolution "240x180"
      audio_codec "libfaac"
      video_bitrate "400k"
      video_codec "mpeg4"
    },
    :extension => "mp4"
  }
}

convert("input_file.avi", :to => PRESETS[:mp4_240x180_400k_aac][:extension]) do
  PRESETS[:mp4_240x180_400k_aac][:block].call
end