Use a symbolic name for the payload size of an RTCP Sender Report packet

Originally committed as revision 10929 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/rtp.c

@@ -32,6 +32,7 @@
 
 //#define DEBUG
 
+#define RTCP_SR_SIZE 28
 
 /* TODO: - add RTCP statistics reporting (should be optional).
 
@@ -983,7 +984,7 @@ static int rtp_write_packet(AVFormatContext *s1, AVPacket *pkt)
     /* XXX: mpeg pts hardcoded. RTCP send every 0.5 seconds */
     rtcp_bytes = ((s->octet_count - s->last_octet_count) * RTCP_TX_RATIO_NUM) /
         RTCP_TX_RATIO_DEN;
-    if (s->first_packet || rtcp_bytes >= 28) {
+    if (s->first_packet || rtcp_bytes >= RTCP_SR_SIZE) {
         rtcp_send_sr(s1, av_gettime());
         s->last_octet_count = s->octet_count;
         s->first_packet = 0;