[nbc] Add an extractor for the main nbc.com site

Some of the videos are encrypted, the f4m downloader doesn’t support them.

youtube_dl/extractor/nbc.py

@@ -6,6 +6,30 @@ from .common import InfoExtractor
 from ..utils import find_xpath_attr, compat_str
 
 
+class NBCIE(InfoExtractor):
+    _VALID_URL = r'http://www\.nbc\.com/[^/]+/video/[^/]+/(?P<id>n?\d+)'
+
+    _TEST = {
+        'url': 'http://www.nbc.com/chicago-fire/video/i-am-a-firefighter/2734188',
+        'md5': '54d0fbc33e0b853a65d7b4de5c06d64e',
+        'info_dict': {
+            'id': 'u1RInQZRN7QJ',
+            'ext': 'flv',
+            'title': 'I Am a Firefighter',
+            'description': 'An emergency puts Dawson\'sf irefighter skills to the ultimate test in this four-part digital series.',
+        },
+    }
+
+    def _real_extract(self, url):
+        mobj = re.match(self._VALID_URL, url)
+        video_id = mobj.group('id')
+        webpage = self._download_webpage(url, video_id)
+        theplatform_url = self._search_regex('class="video-player video-player-full" data-mpx-url="(.*?)"', webpage, 'theplatform url')
+        if theplatform_url.startswith('//'):
+            theplatform_url = 'http:' + theplatform_url
+        return self.url_result(theplatform_url)
+
+
 class NBCNewsIE(InfoExtractor):
     _VALID_URL = r'https?://www\.nbcnews\.com/video/.+?/(?P<id>\d+)'