src/websites/youtube.rb

   1 #
   2 # Copyright Michael Orlitzky
   3 #
   4 # http://michael.orlitzky.com/
   5 #
   6 # This program is free software: you can redistribute it and/or modify
   7 # it under the terms of the GNU General Public License as published by
   8 # the Free Software Foundation, either version 3 of the License, or
   9 # (at your option) any later version.
  10 #
  11 # This program is distributed in the hope that it will be useful,
  12 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14 # GNU General Public License for more details.
  15 #
  16 # http://www.fsf.org/licensing/licenses/gpl.html
  17 #
  18
  19 require 'src/website'
  20 require 'cgi'
  21
  22 class Youtube < Website
  23
  24   VALID_YOUTUBE_URL_REGEX = /^(http:\/\/)?([a-z0-9]+\.)?youtube\.com\/((watch\?v=)|(v\/)|([a-z]+\#[a-z]\/[a-z]\/[0-9]\/))[a-z0-9_\-]+(\&.*)?\#?$/i
  25
  26   def self.owns_url?(url)
  27     return url =~ VALID_YOUTUBE_URL_REGEX
  28   end
  29
  30
  31   def initialize(url)
  32     super
  33
  34     # The @format variable just caches the format of the video we're
  35     # downloading. Storing it will prevent us from having to calculate
  36     # it twice.
  37     @format = 0
  38   end
  39
  40
  41   def get_video_url()
  42     video_id = self.parse_video_id()
  43
  44     # The video's URL (the "page data" URL) may be different from the
  45     # URL that was passed to the program. We support the /v/video_id
  46     # URL format, but that is *not* the main video page where we can
  47     # retrieve the "t" parameter. We can only get that from the
  48     # /watch?v=video_id form.
  49     page_data_url = "http://www.youtube.com/watch?v=#{video_id}"
  50     page_data = self.get_page_data(page_data_url)
  51
  52     # Get the URL map from the page.
  53     fmt_url_map = get_format_url_map(page_data)
  54
  55     # Figure out which formats are available, and if any are,
  56     # choose the best one.
  57     available_formats = fmt_url_map.keys()
  58     desired_format = get_desired_format(available_formats)
  59
  60     # First we cache the format so that when we're asked for the
  61     # video filename later, we don't have to recompute the format.
  62     @format = desired_format
  63
  64     # And then use whatever URL is available for the desired format.
  65     # We assume that all available formats will have an entry in the
  66     # fmt_url_map hash.
  67     video_url = fmt_url_map[desired_format]
  68
  69     return video_url
  70   end
  71
  72
  73   def get_video_filename()
  74     # The format -> extension mapping is available on Wikipedia:
  75     #
  76     #   http://en.wikipedia.org/wiki/YouTube#Quality_and_codecs
  77     #
  78     # The default extension is .flv.
  79     extension = '.flv'
  80
  81     if [18, 22, 35, 37].include?(@format)
  82       extension = '.mp4'
  83     elsif (@format == 17)
  84       extension = '.3gp'
  85     end
  86
  87     return (self.parse_video_id() + extension)
  88   end
  89
  90
  91   protected;
  92
  93   # Get the video id from the URL. Should be relatively easy,
  94   # unless Youtube supports some URL formats of which I'm unaware.
  95   def parse_video_id()
  96     # Both URLs are fairly easy to parse if you handle
  97     # them one at a time. The only tricky situation is when
  98     # parameters like "&hl=en" are tacked on to the end.
  99     # We'll call /watch?v=video_id the "first form."
 100     first_form_video_id_regex = /v=([0-9a-z_\-]+)/i
 101     first_form_matches = first_form_video_id_regex.match(@url)
 102     return first_form_matches[1] if not (first_form_matches.nil? ||
 103                                          first_form_matches.length < 2)
 104
 105     # First form didn't work? Try the second.
 106     second_form_video_id_regex = /\/v\/([0-9a-z_\-]+)/i
 107     second_form_matches = second_form_video_id_regex.match(@url)
 108     return second_form_matches[1] if not (second_form_matches.nil? ||
 109                                           second_form_matches.length < 2)
 110
 111     # ...and the third.
 112     third_form_video_id_regex = /\/([[:alnum:]]+)$/i
 113     third_form_matches = third_form_video_id_regex.match(@url)
 114     return third_form_matches[1] if not (third_form_matches.nil? ||
 115                                          third_form_matches.length < 2)
 116
 117     # If we made it here, we couldn't figure out the video id. Yes,
 118     # this is fatal, since we don't know where the video file is
 119     # located.
 120     raise StandardError.new("Could not parse the video id.")
 121   end
 122
 123
 124
 125   def get_format_url_map(page_data)
 126     # Youtube has implemented a new fmt_url_map that (perhaps
 127     # unsurprisingly) maps formats to video URLs. This makes it
 128     # easyish to parse the video URLs.
 129     url_map = {}
 130     url_map_regex = /fmt_url_map=([^&\"]+)/
 131
 132     matches = url_map_regex.match(page_data)
 133
 134     if (matches.nil? || matches.length < 1)
 135       raise StandardError.new("Could not parse the fmt_url_map Flash variable.")
 136     end
 137
 138     # The map is stored entirely in one Flash variable. The format is
 139     # key|value,key|value,...
 140     maptext = CGI::unescape(matches[1])
 141     entries = maptext.split(',')
 142     entries.each do |entry|
 143       key = entry.split('|')[0].to_i
 144       value = entry.split('|')[1]
 145       url_map[key] = value
 146     end
 147
 148     if (url_map.length < 1)
 149       raise StandardError.new("Could not find any valid format URLs.")
 150     end
 151
 152     return url_map
 153   end
 154
 155
 156   def get_desired_format(available_formats)
 157     # Check for the presence of formats, in order of preference
 158     # (quality). That is, we check for the best formats first. As soon
 159     # as a format is found to be available, we return it as the
 160     # desired format, since the first format we find is going to be
 161     # the best available format.
 162     return 37 if available_formats.include?(37)
 163     return 22 if available_formats.include?(22)
 164     return 35 if available_formats.include?(35)
 165     return 18 if available_formats.include?(18)
 166     return 34 if available_formats.include?(34)
 167     return 17 if available_formats.include?(17)
 168
 169     # Available formats can't be empty (we would have raised an error
 170     # in get_available_formats), so if there's some unknown format
 171     # here we might as well return it as a last resort.
 172     return available_formats[0]
 173   end
 174
 175 end