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     begin
  53       # Get the URL map from the page.
  54       fmt_url_map = get_format_url_map(page_data)
  55
  56       # Figure out which formats are available, and if any are,
  57       # choose the best one.
  58       available_formats = fmt_url_map.keys()
  59       desired_format = get_desired_format(available_formats)
  60
  61       # First we cache the format so that when we're asked for the
  62       # video filename later, we don't have to recompute the format.
  63       @format = desired_format
  64
  65       # And then use whatever URL is available for the desired format.
  66       # We assume that all available formats will have an entry in the
  67       # fmt_url_map hash.
  68       video_url = fmt_url_map[desired_format]
  69       return video_url
  70     rescue StandardError => e
  71       # If at first you do not succeed, maybe someone decided to
  72       # change some shit. This alternate method parses
  73       # url_encoded_fmt_stream_map.
  74       fmt_streams = get_fmt_stream_list(page_data)
  75       video_url = self.choose_best_fmt_stream_url(fmt_streams)
  76
  77       # The "itag" parameter makes the 403 happen.
  78       video_url.gsub!(/itag=\d+&/, '')
  79     end
  80
  81     return video_url
  82   end
  83
  84
  85   def get_video_filename()
  86     # The format -> extension mapping is available on Wikipedia:
  87     #
  88     #   http://en.wikipedia.org/wiki/YouTube#Quality_and_codecs
  89     #
  90     # The default extension is .flv.
  91     extension = '.flv'
  92
  93     if [18, 22, 35, 37].include?(@format)
  94       extension = '.mp4'
  95     elsif (@format == 17)
  96       extension = '.3gp'
  97     end
  98
  99     return (self.parse_video_id() + extension)
 100   end
 101
 102
 103   protected;
 104
 105   def choose_best_fmt_stream_url(fmt_stream_urls)
 106     # Take a list, generated by get_fmt_stream_list(), and choose the
 107     # best URL out of the bunch based on the video format.
 108     fmt_stream_urls.each do |fs|
 109       if fs =~ /video\/mp4/ and fs =~ /quality=large/
 110         return fs
 111       elsif fs =~ /quality=large/
 112         return fs
 113       elsif fs =~ /video\/mp4/
 114         return fs
 115       else
 116         return fs
 117       end
 118     end
 119   end
 120
 121
 122   def unicode_unescape(string)
 123     # Unescape sequences like '\u0026'.
 124     # Ok, only '\u0026' for now.
 125     return string.gsub('\u0026', '&')
 126   end
 127
 128
 129   def get_fmt_stream_list(page_data)
 130     # This is another (new?) method of embedding the video URLs.
 131     # The url_encoded_fmt_stream_map variable contains a list of URLs
 132     # in the form url=foo1,url=foo2...
 133     #
 134     # It looks like the first one in the list is the highest
 135     # quality?  Let's just take that one for now.
 136     fmt_stream_regex = /\"url_encoded_fmt_stream_map\": \"(.+?)\"/
 137
 138     matches = fmt_stream_regex.match(page_data)
 139
 140     if (matches.nil? || matches.length < 2)
 141       raise StandardError.new("Could not parse the url_encoded_fmt_stream_map Flash variable.")
 142     end
 143
 144     urlstring = matches[1]
 145     urlstring.gsub!('url=', '')
 146     urls = urlstring.split(',')
 147
 148     urls.each_index do |idx|
 149       urls[idx] = self.unicode_unescape(urls[idx])
 150       urls[idx] = CGI::unescape(urls[idx])
 151       # Strip off everything after the first space in the URL.
 152       # I don't know why this works, but if we leave the space
 153       # in (encoded, even), Youtube throws us 403 errors.
 154       urls[idx].gsub!(/ .+$/, '')
 155     end
 156
 157     return urls
 158   end
 159
 160
 161   # Get the video id from the URL. Should be relatively easy,
 162   # unless Youtube supports some URL formats of which I'm unaware.
 163   def parse_video_id()
 164     # Both URLs are fairly easy to parse if you handle
 165     # them one at a time. The only tricky situation is when
 166     # parameters like "&hl=en" are tacked on to the end.
 167     # We'll call /watch?v=video_id the "first form."
 168     first_form_video_id_regex = /v=([0-9a-z_\-]+)/i
 169     first_form_matches = first_form_video_id_regex.match(@url)
 170     return first_form_matches[1] if not (first_form_matches.nil? ||
 171                                          first_form_matches.length < 2)
 172
 173     # First form didn't work? Try the second.
 174     second_form_video_id_regex = /\/v\/([0-9a-z_\-]+)/i
 175     second_form_matches = second_form_video_id_regex.match(@url)
 176     return second_form_matches[1] if not (second_form_matches.nil? ||
 177                                           second_form_matches.length < 2)
 178
 179     # ...and the third.
 180     third_form_video_id_regex = /\/([[:alnum:]]+)$/i
 181     third_form_matches = third_form_video_id_regex.match(@url)
 182     return third_form_matches[1] if not (third_form_matches.nil? ||
 183                                          third_form_matches.length < 2)
 184
 185     # If we made it here, we couldn't figure out the video id. Yes,
 186     # this is fatal, since we don't know where the video file is
 187     # located.
 188     raise StandardError.new("Could not parse the video id.")
 189   end
 190
 191
 192
 193   def get_format_url_map(page_data)
 194     # Youtube has implemented a new fmt_url_map that (perhaps
 195     # unsurprisingly) maps formats to video URLs. This makes it
 196     # easyish to parse the video URLs.
 197     url_map = {}
 198     url_map_regex = /fmt_url_map=([^&\"]+)/
 199
 200     matches = url_map_regex.match(page_data)
 201
 202     if (matches.nil? || matches.length < 1)
 203       raise StandardError.new("Could not parse the fmt_url_map Flash variable.")
 204     end
 205
 206     # The map is stored entirely in one Flash variable. The format is
 207     # key|value,key|value,...
 208     maptext = CGI::unescape(matches[1])
 209     entries = maptext.split(',')
 210     entries.each do |entry|
 211       key = entry.split('|')[0].to_i
 212       value = entry.split('|')[1]
 213       url_map[key] = value
 214     end
 215
 216     if (url_map.length < 1)
 217       raise StandardError.new("Could not find any valid format URLs.")
 218     end
 219
 220     return url_map
 221   end
 222
 223
 224   def get_desired_format(available_formats)
 225     # Check for the presence of formats, in order of preference
 226     # (quality). That is, we check for the best formats first. As soon
 227     # as a format is found to be available, we return it as the
 228     # desired format, since the first format we find is going to be
 229     # the best available format.
 230     return 37 if available_formats.include?(37)
 231     return 22 if available_formats.include?(22)
 232     return 35 if available_formats.include?(35)
 233     return 18 if available_formats.include?(18)
 234     return 34 if available_formats.include?(34)
 235     return 17 if available_formats.include?(17)
 236
 237     # Available formats can't be empty (we would have raised an error
 238     # in get_available_formats), so if there's some unknown format
 239     # here we might as well return it as a last resort.
 240     return available_formats[0]
 241   end
 242
 243 end