-        manifest_url += '?hdcore=2.10.3'
-        manifestXml = self._download_webpage(manifest_url, video_id,
-                                             u'Downloading XML manifest',
-                                             u'Unable to download video info XML')
-
-        adoc = xml.etree.ElementTree.fromstring(manifestXml)
-        try:
-            media_node = adoc.findall('./{http://ns.adobe.com/f4m/1.0}media')[0]
-            node_id = media_node.attrib['url']
-            video_id = adoc.findall('./{http://ns.adobe.com/f4m/1.0}id')[0].text
-        except IndexError as err:
-            raise ExtractorError(u'Invalid manifest file')
+        if next_url.endswith(u'manifest.f4m'):
+            manifest_url = next_url + '?hdcore=2.10.3'
+            adoc = self._download_xml(manifest_url, video_id,
+                                         u'Downloading XML manifest',
+                                         u'Unable to download video info XML')