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Pepp77 (Vendor) (OP)
6 Oct 11 5:03
Hi All

We have a customer that are experiencing problems with distorted voicemail messages left for them.

Originally the customer was on a 406v2 with embedded voicemail on version 4.  They were upgraded to version 5, no difference, then we replaced the embedded voicemail, still no change.  We then replaced the main control unit to an IP500 version 2 again with embedded voicemail, still no change.  We then swapped out an external DS module as it seemed to be affecting users who were connected to this, however still no change.

We also turned off re-invite supported on the SIP trunks, no change, turned the non-linear process mode to disabled, no change and added Conference_DSP_TX_GAIN=-4 to the no users source numbers tab, and again no change.

I wasnt involved in most of the testing for this, but have been investigating today and believe the issue started when their ISDN DDI numbers were ported to Gamma Myinbound and then on there forwarded to individual DDI number on Gamma SIP.

No issues have been reported at all with call quality when they actually answer calls only when the calls go to voicemail (and not every message left either).

The SIP trunks are set to automatic compression mode and user offerers preferred codec is ticked.

I am going to try turning the offerers codec off today.

Okay so did tests between typing the above and pressing post so thought I would add this update.

Changing the offerers codec made no difference both with it on and with it off used G711 as the codec.

I then tested by pointing an ISDN DDI that they did have to mytest extension and left a voicemail and it was perfect so it appears that the issue is being caused by calls coming in on the Gamma SIP trunks.

So need some ideas on what else I can try.



hairlessupportmonkey (IS/IT--Management)
6 Oct 11 5:05
might be an issue with the IPO - swapped that out yet? smile

General Geek

Pepp77 (Vendor) (OP)
6 Oct 11 5:08
Yep from a 406v2 to a 500v2.


tlpeter (Programmer)
6 Oct 11 5:11
What software version?
6.0 has issues with EVM.


I'm not insane, my mother had me tested!

hairlessupportmonkey (IS/IT--Management)
6 Oct 11 5:15
sorry - you did say that in your OP you swapped it.

seen this before, but normally rebooting the switch solves it in my case.

so, 406v2 with embedded - distorted.
ip500v2 with new SD card embedded VM distorted

what ip400 components did you you put in the ip500 - e.g vcm card?

General Geek

Pepp77 (Vendor) (OP)
6 Oct 11 5:48
They had a VCM 16 in the old 406 - when we swapped to the 500v2 we used all new parts - so a new VCM 32 was installed.

The only things we moved across were the external expansion modules and as I said we have also swapped out the DS unit that the extensions reporting the issues were on.


tlpeter (Programmer)
6 Oct 11 5:55
Pepp77, what version is the ip500v2 on ?


I'm not insane, my mother had me tested!

Pepp77 (Vendor) (OP)
6 Oct 11 5:57
Sorry its on 7.0(23)


tlpeter (Programmer)
6 Oct 11 6:00
Does this happen all the time?
I had this problem with an AA and an external transfer with not enough lines.
After a certain amount of trying to forward the call then the EVM became distorted.


I'm not insane, my mother had me tested!

nicka29 (TechnicalUser)
6 Oct 11 6:03

I had exactly the same problem with Gamma and it took nearly 6 months to resolve.
The issie lies with their gateway. Once they put me onto their new platform it stopped.
The amount of hours it took to prove it wanst the IP Office was unbelievable. To prove it wasnt the IPO I had to be on site when the voicemail occured with a wireshark trace running from our network and Gamma had a trace running their end. Once we both had a trace the call was already getting distorted before it hit the IPO. By this time like yourself we had completly change the network/IPO and all cards in the system and the voicemail pc.
I am having the same issue at another customer as we speak and Gamma are wanting me to do all these tests again and ive told them to just put us on their new platform

Hope this helps

Pepp77 (Vendor) (OP)
6 Oct 11 6:07
Im not sure if its affecting all voicemails or not - we have had reports now from numerous people on site.

when we added the Conference_DSP entry it seemed to improve, but I placed 3 test calls this morning direct to an offline extension and all 3 messages were bitty with missing words here and there (I monitored the actual calls and the stats were fine, RTD between 0 and 11ms, jitter at 1-2ms max and packet loss less than or about 1%).

Then when I placed a fourth test call in via an ISDN DDI number instead of a SIP ddi number the issue disappeared.

There are no autoattendants and the two most recent people to report it have no diverts/forwards in place.


tlpeter (Programmer)
6 Oct 11 6:10
What codec is the sip provider using?
Do you use Alaw or Ulaw on your system?
Does the sip provider use the same?


I'm not insane, my mother had me tested!

Pepp77 (Vendor) (OP)
6 Oct 11 6:26
nicka29 - Interesting - do you know what the new platform was that they moved you to as we are on

TLPeter - Gamma is set up to use G711 A and the system is set to ALaw.  All calls using the SIP use G711A (whether use offerers preferred codec is on or off).


Pepp77 (Vendor) (OP)
6 Oct 11 6:39
Nick - sorry just to confirm normal calls were fine - it was only voicemail messages being affected?


Pepp77 (Vendor) (OP)
6 Oct 11 7:40
And the plot thickens.

Did a new install last weekend onto an IP500v2 also using Gamma SIP trunks for incoming calls (The ISDN was delayed) and they have reported problems with voicemails being rubbish today.

Nick - any chance you can let me have the reference number you got from Gamma for this issue, we can then use it to get our account manager to get both our accounts moved.



Pepp77 (Vendor) (OP)
6 Oct 11 9:17
And even more interesting we have Gamma SIP trunks but only use them for outgoing so I thought I would point the number we have to my extension and make some test calls.

When called and answered the quality is fine, when called and I send it to voicemail the voicemail is all distorted, bitty and missing things.

So I reckon I have done enough to prove this to Gamma SIP - now just to get Gamma to agree.


Pepp77 (Vendor) (OP)
6 Oct 11 10:36
Nick - sorry another question, do you use registration or IP address on your Gamma SIP trunks?


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