ArteTVIE: extract the video with the correct language

Some urls from the French version of the page could download the German version.

Also instead of extracting the json url from the webpage, build it to skip the download

youtube_dl/extractor/arte.py

@@ -16,7 +16,7 @@ class ArteTvIE(InfoExtractor):
     www.arte.tv/guide, the extraction process is different for each one.
     The videos expire in 7 days, so we can't add tests.
     """
-    _EMISSION_URL = r'(?:http://)?www\.arte.tv/guide/(?:fr|de)/(?:(?:sendungen|emissions)/)?(?P<id>.*?)/(?P<name>.*?)(\?.*)?'
+    _EMISSION_URL = r'(?:http://)?www\.arte.tv/guide/(?P<lang>fr|de)/(?:(?:sendungen|emissions)/)?(?P<id>.*?)/(?P<name>.*?)(\?.*)?'
     _VIDEOS_URL = r'(?:http://)?videos.arte.tv/(?:fr|de)/.*-(?P<id>.*?).html'
     _LIVE_URL = r'index-[0-9]+\.html$'
 
@@ -57,10 +57,11 @@ class ArteTvIE(InfoExtractor):
         mobj = re.match(self._EMISSION_URL, url)
         if mobj is not None:
             name = mobj.group('name')
+            lang = mobj.group('lang')
             # This is not a real id, it can be for example AJT for the news
             # http://www.arte.tv/guide/fr/emissions/AJT/arte-journal
             video_id = mobj.group('id')
-            return self._extract_emission(url, video_id)
+            return self._extract_emission(url, video_id, lang)
 
         mobj = re.match(self._VIDEOS_URL, url)
         if mobj is not None:
@@ -72,10 +73,9 @@ class ArteTvIE(InfoExtractor):
             # self.extractLiveStream(url)
             # return
 
-    def _extract_emission(self, url, video_id):
+    def _extract_emission(self, url, video_id, lang):
         """Extract from www.arte.tv/guide"""
-        webpage = self._download_webpage(url, video_id)
+        json_url = 'http://org-www.arte.tv/papi/tvguide/videos/stream/player/F/%s_PLUS7-F/ALL/ALL.json' % video_id
-        json_url = self._html_search_regex(r'arte_vp_url="(.*?)"', webpage, 'json url')
 
         json_info = self._download_webpage(json_url, video_id, 'Downloading info json')
         self.report_extraction(video_id)
@@ -91,6 +91,16 @@ class ArteTvIE(InfoExtractor):
                      }
 
         formats = player_info['VSR'].values()
+        def _match_lang(f):
+            # Return true if that format is in the language of the url
+            if lang == 'fr':
+                l = 'F'
+            elif lang == 'de':
+                l = 'A'
+            regexes = [r'VO?%s' % l, r'V%s-ST.' % l]
+            return any(re.match(r, f['versionCode']) for r in regexes)
+        # Some formats may not be in the same language as the url
+        formats = filter(_match_lang, formats)
         # We order the formats by quality
         formats = sorted(formats, key=lambda f: int(f['height']))
         # Pick the best quality