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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Hi,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>In our load test, we found that the new RTP auto_flush and
hot_socket code after version 1.<font color=navy><span style='color:navy'>0</span></font>4
<font color=navy><span style='color:navy'>seems to </span></font>cause voice
quality problem. We were stress testing Freeswitch with 250 channels using
codec G.711u and iLBC. The RTP auto_flush <font color=navy><span
style='color:navy'>appear</span></font>ed to be trigged <font color=navy><span
style='color:navy'>very </span></font>frequently. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'>Because our system is under load and socket buffer <font
color=navy><span style='color:navy'>for RTP stream </span></font>sometimes
accumulate<font color=navy><span style='color:navy'>d</span></font> a few
packets before the channel can handle it. When this happened, the RTP
auto_flush and hot_socket mechanism seem<font color=navy><span
style='color:navy'>ed</span></font> sending <font color=navy><span
style='color:navy'>those </span></font>accumulated packets in a very short
interval. However <font color=navy><span style='color:navy'>after this burst,
the RTP stream receiving will wait for 80-100ms before receiving and sending another
RTP packet. To find out why this can happen, We looked at the RTP part of Freeswitch
code and found </span></font>th<font color=navy><span style='color:navy'>at</span></font>
<font color=navy><span style='color:navy'>inside the RTP read, during auto RTP
flush, it will call </span></font>switch_core_timer_sync() function<font
color=navy><span style='color:navy'>.</span></font> <font color=navy><span
style='color:navy'>This will</span></font> add 3 to the timer reference count
and the next switch_core_timer_next() call will add another 1 to timer
reference. This caused the next RTP receiving being delayed 80-100ms. This
80-100ms delay for RTP receiving caused 4-5 packets being accumulated in socket
buffer again. And it will soon trigger another auto_flush for RTP stream. As
the result, we saw a lot of short burst in the RTP stream, which caused voice
quality problem.<o:p></o:p></span></font></p>
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