Summary:ASTERISK-04191: Extreme jitters and sounds garbling
Reporter:nirsim (nirsim)Labels:
Date Opened:2005-05-16 13:50:12Date Closed:2011-06-07 14:10:39
Versions:Frequency of
Description:Ok, I'm not sure if this one belongs in the IAX section or the SIP section, so I'll try it here, and the guys up stairs can move it to where ever they need.

The setup is as following:

PSTN1 -> * -> IAX2/GSM -> * -> SIP/ULAW -> VERAZ -> PSTN2

The problem is that i'm experiencing extreme jitters when calling from PSTN1 to PSTN2 via the boxes. Now, I've tried modifying the setup to the following:

PSTN1 -> * -> SIP/iLBC -> * -> SIP/ULAW -> VERAZ - PSTN2

Results where the same, jitters all the way.

Now, the strange issue is that a different box that I have, which is connected with the first setup, and utilizs the same asterisk CVS vresion, doesn't suffer from the jitters.

If anyone has a method for me to generate more information to attach to this bug report, if indeed it is a bug report.

 Nir S
Comments:By: Michael Jerris (mikej) 2005-05-17 21:48:03

Is the jitter only on the audio going one way?  Jitterbuffers should be applied in the end of the chain, and not on inbetween voip hops.  In fact, the new jitterbuffer intentionally does NOT run when two voip calls are bridged.  If your problem is hearing jitter onthe pstn2 side, it is th responisbility of the VERAZ to provide the jitterbuffering, if it is on the PST1 side, asterisk would have to perform it, so it is important too know.  As to what is causing this, are these lines all local network or across a WAN or inet.  If it is all local and you have the issue on one box and not the other, I would be looking at your hardware (perhaps a bad NIC or some other issue.)  Please provide some additional information about which side hears the jitter, what the network looks like, and if this is only an issue with one piece of hardware, but works fine on the other, details of the hardware involved.

By: nirsim (nirsim) 2005-05-18 02:35:18

Hi Mike,

 Well, I'll draw the setup again:

 PSTN1 -> E1/PRI -> *1 -> IAX/GSM/WAN -> *2 -> SIP/ULAW/LAN -> VERAZ -> PSTN2

 The jitters are experienced on both, at a fairly consistent rate,
however, totally sporadic in terms of where it is heard. It can onetime
be experienced on PSTN1 and a few seconds later on PSTN2.

 If I understand what you write, you mean I should enable Jitter buffering only on *1 as a test, and see what happens, while disabling Jitter buffers on *2, right ?

Nir S

By: Michael Jerris (mikej) 2005-05-18 02:42:11

as for the jitter you hear from the pstn2 side, asterisk won't do anything for you, the veraz device is the end device and it will need to de-jitter the packets coming in.  You don't want to have jitterbuffer running on briged voip channels becuase it is just doing a job that will need to done again at the next hop.  The IAX new jitterbuffer on 1 may be able to do somthing for you on the receiving pstn1 side.

By: Michael Jerris (mikej) 2005-05-25 21:56:42

We need followup on this or it will have to be closed.

By: nirsim (nirsim) 2005-05-29 04:08:15

Well, we had managed to narrow down the jitters to a possible cause related either to the VERAZ switch located at PSTN2 side or a network related jitter between *1 and *2.

Question, is there a signaling/codec combination that would reduce audioable jitters to a minimum?

By: Michael Jerris (mikej) 2005-05-29 08:31:56

try forcejitterbuffer=yes on IAX.  You will both get jitterbuffer running for the WAN link, and be able to look at the jitter stats on that link

By: Michael Jerris (mikej) 2005-06-19 12:41:06

No response to questions.  It appears that this is not an asterisk, but a network issue.  If you continue to have this issue, please re-open the bug.