+            webpage, 'json vp url', default=None)
+        if not json_url:
+            iframe_url = self._html_search_regex(
+                r'<iframe[^>]+src=(["\'])(?P<url>.+\bjson_url=.+?)\1',
+                webpage, 'iframe url', group='url')
+            json_url = compat_parse_qs(
+                compat_urllib_parse_urlparse(iframe_url).query)['json_url'][0]