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Fix the calculation of the RTT for RTCP. The previous code would result in

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oscillating and incorrect data.  Additionally, the RTT would sometimes report
negative values due to incorrect calculations.
(issue #9601, patch from davetroy)


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@65842 65c4cc65-6c06-0410-ace0-fbb531ad65f3
This commit is contained in:
Russell Bryant
2007-05-24 14:49:05 +00:00
parent e4f9cc15e6
commit f32662deb4
1 changed files with 37 additions and 19 deletions
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56
main/rtp.c
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@@ -831,10 +831,10 @@ struct ast_frame *ast_rtcp_read(struct ast_rtp *rtp)
struct timeval now; struct timeval now;
unsigned int length; unsigned int length;
int rc; int rc;
double rtt = 0; double rttsec;
double a; uint64_t rtt;
double dlsr; unsigned int dlsr;
double lsr; unsigned int lsr;
unsigned int msw; unsigned int msw;
unsigned int lsw; unsigned int lsw;
unsigned int comp; unsigned int comp;
@@ -914,26 +914,44 @@ struct ast_frame *ast_rtcp_read(struct ast_rtp *rtp)
break; break;
/* Intentional fall through */ /* Intentional fall through */
case RTCP_PT_RR: case RTCP_PT_RR:
/* This is the place to calculate RTT */
/* Don't handle multiple reception reports (rc > 1) yet */ /* Don't handle multiple reception reports (rc > 1) yet */
/* Calculate RTT per RFC */
gettimeofday(&now, NULL); gettimeofday(&now, NULL);
timeval2ntp(now, &msw, &lsw); timeval2ntp(now, &msw, &lsw);
/* Use the one we sent them in our SR instead, rtcp->txlsr could have been rewritten if the dlsr is large */ if (ntohl(rtcpheader[i + 4]) && ntohl(rtcpheader[i + 5])) { /* We must have the LSR && DLSR */
if (ntohl(rtcpheader[i + 4])) { /* We must have the LSR */
comp = ((msw & 0xffff) << 16) | ((lsw & 0xffff0000) >> 16); comp = ((msw & 0xffff) << 16) | ((lsw & 0xffff0000) >> 16);
a = (double)((comp & 0xffff0000) >> 16) + (double)((double)(comp & 0xffff)/1000000.); lsr = ntohl(rtcpheader[i + 4]);
lsr = (double)((ntohl(rtcpheader[i + 4]) & 0xffff0000) >> 16) + (double)((double)(ntohl(rtcpheader[i + 4]) & 0xffff) / 1000000.); dlsr = ntohl(rtcpheader[i + 5]);
dlsr = (double)(ntohl(rtcpheader[i + 5])/65536.); rtt = comp - lsr - dlsr;
rtt = a - dlsr - lsr;
if (rtt >= 0) { /* Convert end to end delay to usec (keeping the calculation in 64bit space)
rtp->rtcp->accumulated_transit += rtt; sess->ee_delay = (eedelay * 1000) / 65536; */
rtp->rtcp->rtt = rtt; if (rtt < 4294) {
if (rtp->rtcp->maxrtt < rtt) rtt = (rtt * 1000000) >> 16;
rtp->rtcp->maxrtt = rtt; } else {
if (rtp->rtcp->minrtt > rtt) rtt = (rtt * 1000) >> 16;
rtp->rtcp->minrtt = rtt; rtt *= 1000;
}
rtt = rtt / 1000.;
rttsec = rtt / 1000.;
if (comp - dlsr >= lsr) {
rtp->rtcp->accumulated_transit += rttsec;
rtp->rtcp->rtt = rttsec;
if (rtp->rtcp->maxrtt<rttsec)
rtp->rtcp->maxrtt = rttsec;
if (rtp->rtcp->minrtt>rttsec)
rtp->rtcp->minrtt = rttsec;
} else {
ast_verbose("Internal RTCP NTP clock skew detected: "
"lsr=%u, now=%u, dlsr=%u (%d:%03dms), "
"diff=%d",
lsr, comp, dlsr, dlsr / 65536,
(dlsr % 65536) * 1000 / 65536,
dlsr - (comp - lsr));
} }
} }
rtp->rtcp->reported_jitter = ntohl(rtcpheader[i + 3]); rtp->rtcp->reported_jitter = ntohl(rtcpheader[i + 3]);
rtp->rtcp->reported_lost = ntohl(rtcpheader[i + 1]) & 0xffffff; rtp->rtcp->reported_lost = ntohl(rtcpheader[i + 1]) & 0xffffff;
if (rtcp_debug_test_addr(&sin)) { if (rtcp_debug_test_addr(&sin)) {
@@ -945,7 +963,7 @@ struct ast_frame *ast_rtcp_read(struct ast_rtp *rtp)
ast_verbose(" Last SR(our NTP): %lu.%010lu\n",(unsigned long) ntohl(rtcpheader[i + 4]) >> 16,((unsigned long) ntohl(rtcpheader[i + 4]) << 16) * 4096); ast_verbose(" Last SR(our NTP): %lu.%010lu\n",(unsigned long) ntohl(rtcpheader[i + 4]) >> 16,((unsigned long) ntohl(rtcpheader[i + 4]) << 16) * 4096);
ast_verbose(" DLSR: %4.4f (sec)\n",ntohl(rtcpheader[i + 5])/65536.0); ast_verbose(" DLSR: %4.4f (sec)\n",ntohl(rtcpheader[i + 5])/65536.0);
if (rtt) if (rtt)
ast_verbose(" RTT: %f(sec)\n", rtt); ast_verbose(" RTT: %lu(sec)\n", rtt);
} }
break; break;
case RTCP_PT_FUR: case RTCP_PT_FUR: