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rtpjitterbuffer: improved rtx-rtt averaging

Browse source 
The basic idea is this:
1. For *larger* rtx-rtt, weigh a new measurement as before
2. For *smaller* rtx-rtt, be a bit more conservative and weigh a bit less
3. For very large measurements, consider them "outliers"
   and count them a lot less

The idea being that reducing the rtx-rtt is much more harmful then
increasing it, since we don't want to be underestimating the rtt of the
network, and when using this number to estimate the latency you need for
you jitterbuffer, you would rather want it to be a bit larger then a bit
smaller, potentially losing rtx-packets. The "outlier-detector" is there
to prevent a single skewed measurement to affect the outcome too much.
On wireless networks, these are surprisingly common.

https://bugzilla.gnome.org/show_bug.cgi?id=769768
This commit is contained in:
Havard Graff 2016-08-11 23:07:44 +02:00 committed by Olivier Crête
parent f8238f0a9f
commit f440b074b1
2 changed files with 28 additions and 5 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

31
gst/rtpmanager/gstrtpjitterbuffer.c
View file

@ -3543,6 +3543,32 @@ get_rtx_retry_period (GstRtpJitterBufferPrivate * priv,
return rtx_retry_period;
}
/*
1. For *larger* rtx-rtt, weigh a new measurement as before (1/8th)
2. For *smaller* rtx-rtt, be a bit more conservative and weigh a bit less (1/16th)
3. For very large measurements (> avg * 2), consider them "outliers"
and count them a lot less (1/48th)
*/
static void
update_avg_rtx_rtt (GstRtpJitterBufferPrivate * priv, GstClockTime rtt)
{
gint weight;
if (priv->avg_rtx_rtt == 0) {
priv->avg_rtx_rtt = rtt;
return;
}
if (rtt > 2 * priv->avg_rtx_rtt)
weight = 48;
else if (rtt > priv->avg_rtx_rtt)
weight = 8;
else
weight = 16;
priv->avg_rtx_rtt = (rtt + (weight - 1) * priv->avg_rtx_rtt) / weight;
}
static void
update_rtx_stats (GstRtpJitterBuffer * jitterbuffer, TimerData * timer,
GstClockTime dts, gboolean success)
@ -3574,10 +3600,7 @@ update_rtx_stats (GstRtpJitterBuffer * jitterbuffer, TimerData * timer,
if (timer->num_rtx_retry == timer->num_rtx_received &&
dts != GST_CLOCK_TIME_NONE && dts > timer->rtx_last) {
delay = dts - timer->rtx_last;
if (priv->avg_rtx_rtt == 0)
priv->avg_rtx_rtt = delay;
else
priv->avg_rtx_rtt = (delay + 7 * priv->avg_rtx_rtt) / 8;
update_avg_rtx_rtt (priv, delay);
} else {
delay = 0;
}

2
tests/check/elements/rtpjitterbuffer.c
View file

@ -1796,7 +1796,7 @@ GST_START_TEST (test_rtx_duplicate_packet_updates_rtx_stats)
"rtx-per-packet", G_TYPE_DOUBLE, 1.0,
"rtx-rtt", G_TYPE_UINT64, (guint64)
/* Use the rtx-rtt formula. Can be subject to change though. */
((now - rtx_request_6) + 7 * (now - rtx_request_7)) / 8, NULL)));
((now - rtx_request_6) + 47 * (now - rtx_request_7)) / 48, NULL)));
gst_object_unref (testclock);
gst_harness_teardown (h);