rtpdec: Increase max rtp packet size to 8192

Fixes Ticket2314
Fixes connecting to "Ceton InfiniTV4 PCIe & USB"
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/rtpdec.h

@@ -33,7 +33,7 @@ typedef struct PayloadContext PayloadContext;
 typedef struct RTPDynamicProtocolHandler RTPDynamicProtocolHandler;
 
 #define RTP_MIN_PACKET_LENGTH 12
-#define RTP_MAX_PACKET_LENGTH 1500
+#define RTP_MAX_PACKET_LENGTH 8192
 
 #define RTP_REORDER_QUEUE_DEFAULT_SIZE 10