[Asterisk-Dev] IAX2 Jitter Buffer questions

Andrew Kohlsmith akohlsmith-asterisk at benshaw.com
Tue Jan 20 09:54:18 MST 2004

> This is going to be a kind of meandering email, it's mostly a brain dump
> of trying to understand what's going on.  I have been trying to help fix
> a problem with my one asterisk server.  Calls through Voicepulse are
> mostly fine but sometimes the jitter on my line causes the GSM call to
> sound like absolute shit.

Just an update and some data points

there is a call currently in progress.  iax2 show channels shows the lag at 
about 70-90ms, with ~20ms jitter.  Jumps as high as 260ms jitter (with the 
lag following).

Now I thought that with my maxexcessbuffer set to 250ms that I would 
MAINTAIN 250ms of lag.  This doesn't seem to be the case, or perhaps 
chan_iax2's buggy and doesn't actually take that into account.

I entered "iax2 set jitter 100" and now my lag is pretty much locked at 
136ms with jitter in the 20-90ms range (but sometimes jumping)

I'm waiting for the guy talking to get off the phone so I can ask him about 
the quality but it would seem that my suspicions about maxexcessbuffer not 
being taken into account are true.

I just tried "iax2 set jitter 200" and 250 but the lag hasn't moved at all.  
In fact it got a little lower (128ms)...  

Is there any definitive information on how to adjust these settings and how 
to monitor their effect??


More information about the asterisk-dev mailing list