If no type was found using the typefind functions, try doing an upstream

URI query to guess the type from the extension. See #566661.

plugins/elements/gsttypefindelement.c

@@ -606,6 +606,71 @@ gst_type_find_element_setcaps (GstPad * pad, GstCaps * caps)
   return TRUE;
 }
 
+static GstCaps *
+gst_type_find_guess_by_extension (GstTypeFindElement *typefind, GstPad *pad,
+    GstTypeFindProbability *probability)
+{
+  GstQuery *query;
+  gchar *uri;
+  size_t len;
+  gint find;
+  GstCaps *caps;
+
+  query = gst_query_new_uri ();
+
+  /* try getting the caps with an uri query and from the extension */
+  if (!gst_pad_peer_query (pad, query))
+    goto peer_query_failed;
+
+  gst_query_parse_uri (query, &uri);
+  if (uri == NULL)
+    goto no_uri;
+
+  GST_DEBUG_OBJECT (typefind, "finding extension of %s", uri);
+
+  /* find the extension on the uri, this is everything after a '.' */
+  len = strlen (uri);
+  find = len - 1;
+
+  while (find >= 0) {
+    if (uri[find] == '.')
+      break;
+    find--;
+  }
+  if (find < 0) 
+    goto no_extension;
+
+  GST_DEBUG_OBJECT (typefind, "found extension %s", &uri[find+1]);
+
+  caps = gst_type_find_helper_for_extension (GST_OBJECT_CAST (typefind), &uri[find+1]);
+  if (caps)
+    *probability = GST_TYPE_FIND_MAXIMUM;
+
+  gst_query_unref (query);
+
+  return caps;
+
+  /* ERRORS */
+peer_query_failed:
+  {
+    GST_WARNING_OBJECT (typefind, "failed to query peer uri");
+    gst_query_unref (query);
+    return NULL;
+  }
+no_uri:
+  {
+    GST_WARNING_OBJECT (typefind, "could not parse the peer uri");
+    gst_query_unref (query);
+    return NULL;
+  }
+no_extension:
+  {
+    GST_WARNING_OBJECT (typefind, "could not find uri extension in %s", uri);
+    gst_query_unref (query);
+    return NULL;
+  }
+}
+
 static GstFlowReturn
 gst_type_find_element_chain (GstPad * pad, GstBuffer * buffer)
 {
@@ -752,9 +817,11 @@ gst_type_find_element_activate (GstPad * pad)
      2. try to pull type find.
      3. deactivate pull mode.
      4. src pad might have been activated push by the state change. deactivate.
-     5. if we didn't find any caps, fail.
+     5. if we didn't find any caps, try getting the uri extension by doing an uri
-     6. emit have-type; maybe the app connected the source pad to something.
+        query.
-     7. if the sink pad is activated, we are in pull mode. succeed.
+     6. if we didn't find any caps, fail.
+     7. emit have-type; maybe the app connected the source pad to something.
+     8. if the sink pad is activated, we are in pull mode. succeed.
      otherwise activate both pads in push mode and succeed.
    */
 
@@ -803,6 +870,11 @@ gst_type_find_element_activate (GstPad * pad)
   gst_pad_activate_push (typefind->src, FALSE);
 
   /* 5 */
+  if (!found_caps || probability < typefind->min_probability) {
+    found_caps = gst_type_find_guess_by_extension (typefind, pad, &probability);
+  }
+
+  /* 6 */
   if (!found_caps || probability < typefind->min_probability) {
     GST_ELEMENT_ERROR (typefind, STREAM, TYPE_NOT_FOUND, (NULL), (NULL));
     gst_caps_replace (&found_caps, NULL);
@@ -810,13 +882,13 @@ gst_type_find_element_activate (GstPad * pad)
   }
 
 done:
-  /* 6 */
+  /* 7 */
   g_signal_emit (typefind, gst_type_find_element_signals[HAVE_TYPE],
       0, probability, found_caps);
   gst_caps_unref (found_caps);
   typefind->mode = MODE_NORMAL;
 
-  /* 7 */
+  /* 8 */
   if (gst_pad_is_active (pad))
     return TRUE;
   else {