rtsp/rtp_read_header: Use RTP_MAX_PACKET_LENGTH instead of 1500

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/rtsp.c

@@ -2134,7 +2134,7 @@ static int rtp_probe(AVProbeData *p)
 
 static int rtp_read_header(AVFormatContext *s)
 {
-    uint8_t recvbuf[1500];
+    uint8_t recvbuf[RTP_MAX_PACKET_LENGTH];
     char host[500], sdp[500];
     int ret, port;
     URLContext* in = NULL;