Add --mobile-version program option

youtube-dl

@@ -437,7 +437,7 @@ class YoutubeIE(InfoExtractor):
 			format_param = params.get('format', None)
 
 		# Extension
-		video_extension = {'18': 'mp4'}.get(format_param, 'flv')
+		video_extension = {'18': 'mp4', '17': '3gp'}.get(format_param, 'flv')
 
 		# Normalize URL, including format
 		normalized_url = 'http://www.youtube.com/watch?v=%s' % video_id
@@ -537,6 +537,8 @@ if __name__ == '__main__':
 				dest='format', metavar='FMT', help='video format code')
 		parser.add_option('-b', '--best-quality',
 				action='store_const', dest='video_format', help='alias for -f 18', const='18')
+		parser.add_option('-m', '--mobile-version',
+				action='store_const', dest='video_format', help='alias for -f 17', const='17')
 		parser.add_option('-i', '--ignore-errors',
 				action='store_true', dest='ignoreerrors', help='continue on download errors', default=False)
 		(opts, args) = parser.parse_args()