rtspsrc: select multicast transports in a smarter way

When we see a multicast address in the SDP connection, only try to negotiate a
multicast transport with the server.

Fixes #634093

gst/rtsp/gstrtspsrc.c

@@ -915,9 +915,14 @@ gst_rtspsrc_do_stream_connection (GstRTSPSrc * src, GstRTSPStream * stream,
   else
     return;
 
-  /* save address, FIXME, check for multicast */
+  /* save address */
   g_free (stream->destination);
   stream->destination = g_strdup (conn->address);
+
+  /* check for multicast */
+  stream->is_multicast =
+      gst_sdp_address_is_multicast (conn->nettype, conn->addrtype,
+      conn->address);
   stream->ttl = conn->ttl;
 }
 
@@ -4849,6 +4854,10 @@ gst_rtspsrc_setup_streams (GstRTSPSrc * src)
     GST_DEBUG_OBJECT (src, "doing setup of stream %p with %s", stream,
         stream->conninfo.location);
 
+    /* if we have a multicast connection, only suggest multicast from now on */
+    if (stream->is_multicast)
+      protocols &= GST_RTSP_LOWER_TRANS_UDP_MCAST;
+
   next_protocol:
     /* first selectable protocol */
     while (protocol_masks[mask] && !(protocols & protocol_masks[mask]))

gst/rtsp/gstrtspsrc.h

@@ -145,6 +145,7 @@ struct _GstRTSPStream {
 
   /* destination */
   gchar        *destination;
+  gboolean      is_multicast;
   guint         ttl;
 };