[gstreamer-bugs] [Bug 565319] New: rtpjitterbuffer: bursty reception can cause time to be reversed
GStreamer (bugzilla.gnome.org)
bugzilla-daemon at bugzilla.gnome.org
Mon Dec 22 01:31:12 PST 2008
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GStreamer | gst-plugins-bad | Ver: 0.10.21
Summary: rtpjitterbuffer: bursty reception can cause time to be
reversed
Product: GStreamer
Version: 0.10.21
Platform: Other
OS/Version: All
Status: UNCONFIRMED
Severity: normal
Priority: Normal
Component: gst-plugins-bad
AssignedTo: gstreamer-bugs at lists.sourceforge.net
ReportedBy: arnout at mind.be
QAContact: gstreamer-bugs at lists.sourceforge.net
GNOME version: Unspecified
GNOME milestone: Unspecified
Please describe the problem:
In rtpjitterbuffer's calculate_skew, buffer timestamps are shifted with a skew
value that changes over time. However, it is possible that the skew changes
more than the time between buffers, which causes buffer timestamps to go back
in time.
While running, this is very unlikely to occur due to the large weighting factor
of the running average. It can occur, for example, when network latency
(temporarily) increases, and the skew grows to e.g. 6s. Then, suddenly, all
these packets arrive in a burst, which causes delta (the difference between
sending and receiving clock) to shrink suddenly to e.g. 6ms. The new skew will
then be 6000*124/125 + 6 = 5958ms, and the buffer timestamp is set at 2ms less
than the previous buffer timestamp.
On the other hand, while the window is filling, this can occur very easily.
Indeed, at that point the weighting factor decreases parabolically, so that the
weighting factor approaches 0 when the window fills up. Therefore, when rtp
packets come in in a burst while the window is filling, the skew shrinks
quickly.
Steps to reproduce:
Actual results:
Expected results:
Does this happen every time?
Other information:
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