Summary:ASTERISK-01323: Codec conversion between ulaw and alaw using IAX causes audio gremlins/ lots of clicks
Reporter:chrisorme (chrisorme)Labels:
Date Opened:2004-04-01 07:42:14.000-0600Date Closed:2004-09-25 02:51:26
Versions:Frequency of
Environment:Attachments:( 0) possjitter4.mp3
Description:When audio is shipped over IAX from Ulaw format into Alaw (what we use here in the UK) lots of clicks etc. are heard.
When there is no translation occurs there is no problem.


This usually isn't a problem as we can usually stay within Alaw on IAX but this has always been the case with * and is displayed in both current CVS and stable.
It worries us most as the IAXy currently uses Ulaw and all our systems here are Alaw and therefore we hear this problem on calls and we really like the IAXy otherwise.  
I have tried adjusting the jitter buffer settings but can't eliminate the clicks and am not totally sure what to do for the best with the jitter buffer.
I think these clicks might also appear on other codec translation but only when using IAX (not SIP).
If someone wants to hear this for themselves please send me your email and I will set up a test account using IAX.
Comments:By: chrisorme (chrisorme) 2004-04-01 08:01:10.000-0600

This should have been posted to IAX project not SIP project.. Can anyone move it?

By: twisted (twisted) 2004-04-03 00:48:34.000-0600


By: Brian West (bkw918) 2004-04-03 10:53:13.000-0600

ok if you are going from BOX A to BOX B is it ulaw or alaw?  or what are you doing?  Beacuse it should leave box A in the proper format for B.

Configs and a little more info?

By: chrisorme (chrisorme) 2004-04-03 11:27:41.000-0600

Basically we have :

Clients --(IAX or SIP)-->  office * box ---(IAX/alaw)---> telco provider

a) using an IAXY client with ulaw as the client (and sending to the provider in alaw) gives this problem or

b) using anything as client when we send from the office * box to the provider in ulaw (and he converts it to alaw to put it on our UK PSTN) then we have this nasty clicking.

talking to * with SIP in g729 or gsm or alaw and then sending to the provider with IAX in alaw (what he wants) causes no clicking.

The configs are very simple.

like for the iaxy


and our provider


Basically changing codec when using IAX seems to cause the clicking.
Hope that helps


By: Mark Spencer (markster) 2004-04-08 00:53:26

Is this still a problem?  I assume IAX2?

By: chrisorme (chrisorme) 2004-04-08 04:56:48

It certainly was on 1 April with both stable and CVS.  Yup, IAX2.

Would you like me to test with the latest CVS ie. have changes been made that might have resolved this constant clicking on the line when converting between U and A-law (and also between ADPCM and A-law, when it's worse) ?

We'd love to use the iaxy but we either need GSM/G726-32 or A-law in it or to resolve this clicking arising on this codec translation.

So far we eliminate this clicking by not changing codec over IAX2 which is what causes it but it'd be great if you could solve this.


By: Mark Spencer (markster) 2004-04-14 17:08:15

Can you test again, we'ave made some improvements that may be relevant in CVS as of 4/14/04.

By: chrisorme (chrisorme) 2004-04-15 07:55:54

Echo gone with snom - yeay, thanks loads for the latest CVS! but we still appear to have clicking or whatever it is if we change codec.
attached: possjitter4.mp3 so you can hear the noise for yourself, might help ?

I can't change the CVS that the provider uses though if that matters.  They change the IAX2 to PSTN/E1/T1.

I haven't tested with an IAXY yet though as I couldn't seem to iaxyprov it as it was behind NAT - argh!, tomorrow I should have it back for real hopefully to see how the clicks are...

By: Mark Spencer (markster) 2004-04-15 10:16:57

Who is the provider?

By: chrisorme (chrisorme) 2004-04-15 17:22:12

The clicks virtually disappear (or are at least much improved) when using a different provider.  ie testing instead with a new provider.  Also the new providers timestamps (to my untrained eye) look better too.

I am very very very sorry if I have wasted your time in reporting this, but I don't know what is going wrong with the other provider.  
I would guess it might stem from their possible use of the 12/5/03 CVS of Asterisk maybe ?  Their timestamps (again to my untrained eye) don't look as nice and regular.

edited on: 04-15-04 16:15

edited on: 04-15-04 16:31

By: Mark Spencer (markster) 2004-04-15 17:39:07

This was totally a legitimate bug until just yesterday, so no problem at all.  Hopefully you can e-mail your first provider and ask them to update their Asterisk.  Contact me off the bug tracker if they insist on running -stable instead of -head and i'll try to backport the changes.