/*
* Very first call at application start-up uses half the min
* delay for quicker notification while still allowing some time
* before reporting for randomization and to learn about other
* sources so the report interval will converge to the correct
* interval more quickly. The average RTCP size is initialized
* to 128 octets which is conservative (it assumes everyone else
* is generating SRs instead of RRs: 20 IP + 8 UDP + 52 SR + 48
* SDES CNAME).
*/
if (initial) {
rtcp_min_time /= 2;
*avg_rtcp_size = 128;
}
/*
* If there were active senders, give them at least a minimum
* share of the RTCP bandwidth. Otherwise all participants share
* the RTCP bandwidth equally.
*/
n = members;
if (senders > 0 && senders < members * RTCP_SENDER_BW_FRACTION) {
if (we_sent) {
rtcp_bw *= RTCP_SENDER_BW_FRACTION;
n = senders;
} else {
rtcp_bw *= RTCP_RCVR_BW_FRACTION;
n -= senders;
}
}
/*
* Update the average size estimate by the size of the report
* packet we just sent.
*/
*avg_rtcp_size += (packet_size - *avg_rtcp_size)*RTCP_SIZE_GAIN;
/*
* The effective number of sites times the average packet size is
* the total number of octets sent when each site sends a report.
Schulzrinne, et al Standards Track [Page 70]
RFC 1889 RTP January 1996
* Dividing this by the effective bandwidth gives the time
* interval over which those packets must be sent in order to
* meet the bandwidth target, with a minimum enforced. In that
* time interval we send one report so this time is also our
* average time between reports.
*/
t = (*avg_rtcp_size) * n / rtcp_bw;
if (t < rtcp_min_time) t = rtcp_min_time;
/*
* To avoid traffic bursts from unintended synchronization with
* other sites, we then pick our actual next report interval as a
* random number uniformly distributed between 0.5*t and 1.5*t.
*/
return t * (drand48() + 0.5);
}
A.8 Estimating the Interarrival Jitter
