asterisk users - Dec 2005 - Weird IAX trunking/7960/ILBC quality issue

Greetings all,

I've been doing some testing with a new client's voicemail system from
my
asterisk box at home. I'm using a 7960 (alaw/ulaw) then an IAX2 link between
my server and the client's server.

I've configured IAX settings at both ends as follows: jitterbuffer enabled,
trunking enabled, ILBC/GSM allowed in that order. When listening to the
voice prompts from VoicemailMain at the client's asterisk I hear about one
word in three, very similar to a GSM mobile on the border of its coverage.
Disabling trunking appears to make no difference. Disabling the jitter
buffer appears to solve the problem, but with a connection that's often used
for other things, this is undesirable as a long-term solution.

When I make the same call from a SIP device (GXP2000), the issue disappears
entirely. But the same problem does not occur from the 7960 to a PSTN
gateway (also via IAX2 with exactly the same settings).

To summarize:
7960 -> remote (ILBC + jitterbuffer) = quality problem
SIP -> remote (ILBC + jitterbuffer) = no problem
7960 -> remote (ILBC no jitterbuffer) = no problem

I'm not sure what's to blame here - the 7960 or my IAX settings, or
where to
begin looking for solutions.

Any thoughts?

Regards,

Chris
-- 
C.M. Bagnall, Director, Minotaur I.T. Limited
This email is made from 100% recycled electrons

> 
> Greetings all,
> 
> I've been doing some testing with a new client's voicemail system
from
my
> asterisk box at home. I'm using a 7960 (alaw/ulaw) then an IAX2 link
> between
> my server and the client's server.
> 
> I've configured IAX settings at both ends as follows: jitterbuffer
> enabled,
> trunking enabled, ILBC/GSM allowed in that order. When listening to
the
> voice prompts from VoicemailMain at the client's asterisk I hear about
one
> word in three, very similar to a GSM mobile on the border of its
coverage.
> Disabling trunking appears to make no difference. Disabling the jitter
> buffer appears to solve the problem, but with a connection that's
often
> used
> for other things, this is undesirable as a long-term solution.
> 
> When I make the same call from a SIP device (GXP2000), the issue
> disappears
> entirely. But the same problem does not occur from the 7960 to a PSTN
> gateway (also via IAX2 with exactly the same settings).
> 
> To summarize:
> 7960 -> remote (ILBC + jitterbuffer) = quality problem
> SIP -> remote (ILBC + jitterbuffer) = no problem
> 7960 -> remote (ILBC no jitterbuffer) = no problem
> 
> I'm not sure what's to blame here - the 7960 or my IAX settings, or
where
> to
> begin looking for solutions.
> 
> Any thoughts?
> 
> Regards,
> 
> Chris
> --
> C.M. Bagnall, Director, Minotaur I.T. Limited
> This email is made from 100% recycled electrons
> 
> 
Jitterbuffer is to blame.

hi,

I see in the libpri code that PRI_SWITCH_EUROISDN_T1 is coded different 
than PRI_SWITCH_EUROISDN_E1. What exactly is the T1/EuroISDN and where 
do I find this standard?

J

> Jitterbuffer is to blame.
I feared as much. Thanks for the confirmation.

1) Is this a known issue with ILBC + Jitter Buffer?
2) Why does the same not occur from a SIP handset?
3) Is it "safe" or "wise" to disable the jitterbuffer?

Thanks kindly.

Regards,

Chris
-- 
C.M. Bagnall, Director, Minotaur I.T. Limited
This email is made from 100% recycled electrons