To retrieve raw video ulrs from youtube.

youtube_webm_url.rb

require 'uri'
require 'net/http'
require 'cgi'

class ScrapeYoutube
  @@youtube_url = 'http://www.youtube.com'
  @@youtube_info_path = '/get_video_info?video_id='
  @@key = "url_encoded_fmt_stream_map"
  
  def self.showWebmUrl(video_id)
    map = getVideoInfo(video_id)
    map[@@key].each do |m|
      if (m["type"].start_with?("video/webm")) then
        puts m["url"]
      end
    end
  end

  def self.showInfo(video_id)
    printBody(getVideoInfo(video_id))
  end

  def self.getVideoInfo(video_id)
    url = URI.parse(@@youtube_url+@@youtube_info_path+video_id)
    req = Net::HTTP::Get.new(url.to_s)
    res = Net::HTTP.start(url.host, url.port) {|http|
      http.request(req)
    }
    map = toMap(res.body)
    map[@@key] = parseFmt(map[@@key])
    return map
  end

  def self.printBody(map, indent="")
    map.each_pair do |k, v|
      if (v.kind_of?(Hash)) then
        puts indent + k + " =>"
        printBody(v, " "+indent)
      elsif (v.kind_of?(Array)) then
        puts indent + k + " =>"
        v.each do |e|
          printBody(e, " "+indent)
          puts("")
        end
      else 
        puts indent + k + " => " + v
      end
    end
  end

  def self.toMap(str)
    map = Hash::new
    str.split('&').each do |e|
      ary = e.split('=')
      map[ary[0]] = URI.decode(ary[1] || "")
    end
    return map
  end

  def self.parseFmt(str)
    dst = []
    map = Hash::new
    str.split(',').each do |e|
      dst << toMap(e)
    end
    return dst
  end

end

ScrapeYoutube::showWebmUrl("sPasebVMIW4")
ScrapeYoutube::showInfo("sPasebVMIW4")