+ * @GST_MESSAGE_EXTENDED: Message is an extended message type (see below).
+ * These extended message IDs can't be used directly with mask-based API
+ * like gst_bus_poll() or gst_bus_timed_pop_filtered(), but you can still
+ * filter for GST_MESSAGE_EXTENDED and then check the result for the
+ * specific type. (Since 1.4)
+ * @GST_MESSAGE_DEVICE_ADDED: Message indicating a #GstDevice was added to
+ * a #GstDeviceMonitor (Since 1.4)
+ * @GST_MESSAGE_DEVICE_REMOVED: Message indicating a #GstDevice was removed
+ * from a #GstDeviceMonitor (Since 1.4)