[spiegel] Use centralized sorting

youtube_dl/extractor/common.py

@@ -438,6 +438,11 @@ class InfoExtractor(object):
 
     def _sort_formats(self, formats):
         def _formats_key(f):
+            # TODO remove the following workaround
+            from ..utils import determine_ext
+            if not f.get('ext') and 'url' in f:
+                f['ext'] = determine_ext(f['url'])
+
             preference = f.get('preference')
             if preference is None:
                 preference = 0 if f.get('url', '').startswith('http') else -0.1

youtube_dl/extractor/spiegel.py

@@ -51,9 +51,10 @@ class SpiegelIE(InfoExtractor):
             # Blacklist type 6, it's extremely LQ and not available on the same server
             if n.tag.startswith('type') and n.tag != 'type6'
         ]
-        formats.sort(key=lambda f: f['vbr'])
         duration = float(idoc[0].findall('./duration')[0].text)
 
+        self._sort_formats(formats)
+
         info = {
             'id': video_id,
             'title': video_title,