Don't use tcp_fd if we're not using TCP-based connections (e.g. when

reading direct SDP files to set up UDP-based RTP-streams). Fixes
issue 1713. Patch by Jeremy Morton <ffmpeg game-point net>.

Originally committed as revision 21461 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/rtsp.c

@@ -1457,7 +1457,7 @@ static int udp_read_packet(AVFormatContext *s, RTSPStream **prtsp_st,
                 }
             }
 #if CONFIG_RTSP_DEMUXER
-            if (FD_ISSET(tcp_fd, &rfds)) {
+            if (tcp_fd != -1 && FD_ISSET(tcp_fd, &rfds)) {
                 RTSPMessageHeader reply;
 
                 rtsp_read_reply(s, &reply, NULL, 0);