IP-IVR with G711A

[cukouncukoun]

Good morning all,

we are using IP-IVR with G711U and we will have to change codec to G711A due to our SIP provider will discontinue to supporting U-law codec. All of our prompts on the IVR are on this U-law codec so we thought that we will have to transcode them to A-law and import them again to the IVR before using A-law between IVR and CUBE.

I wanted to test what will happen when we change these codecs directly without changing all of the prompts on the IVR and for my surprise it was working without any issue :-). So my question is how its possible that g711u prompts are normally beeing played in case when call to IVR was established with G711A without any xcoder or MTP inserted by CUCM so media went directly between CUBE and IVR server IP addresses??

Tomas

[Graham Old]

The only thing that fails with G711 a-law is the script recording step, everything else works OK. This causes a lot of problems if you are using call backs and allowing the caller to record a message.

There is very little difference between a-law and u-law. You are supposed to change the format for quality reasons but you won't be able to hear the difference.

Graham

[cukouncukoun]

Graham thanks for answer.I know about g711a limitations with recording step. There is already open bug for this si I hope that this will be resolve soon - I think thats not so hard to resolve it :-).

My main question was about g711U/A changing on the call flow. I know that there is just a little difference between U-law and A-law codecs and voice quality is the same but my question was why U-law prompts could be played through A-law call? Normally CUCM will insert MTP or xcoder to these type of calls for interoperability between both codecs but as I mentioned there was no MTP inserted and media was directly between IVR and CUBE.

Tomas

[Slavik Bialik]

You won't be able to hear u-Low prompts without the service provider sending also u-Law support in the SIP SDP message.

Unless of course you'll use MTP or xcoder. But I would not advise to do it. I'd prefer to convert all prompts from u-Law to a-Law. You can use a free awesome tool called GoldWave, you can create a simple batch that'll convert ALL your prompts in a single job, without going one-by-one and converting them.

[Graham Old]

We should seek clarification on what version you have and how you are using IP-IVR, is it part of an Enterprise system?

From version 9.0(2) CCX and IP-IVR support both G711 u-law and G711 a-law.

We have had a small number of CCX customers move from E1 using G711 u-law as the default codec to a SIP service only offering G711 a-law.

Other than the previously mentioned problem with the script recording step there has been no problems or noticeable audio quality issues.

There is a conversation here

https://community.cisco.com/t5/ip-telephony-and-phones/transcoding-in-cube/m-p/3416006#M367142

about using transcoding on the CUBE to force a call into CCX to use G711 u-law so the record script step works.

Graham

[cukouncukoun]

We are using IVR 11.6 and yes its part of the UCCE. So far we are using U-law and all our prompts on the IVR are on this format.

Codec configured on the CUBE dial-peer pointing to the CUCM is just with A-law so when I tried a call I thought that CUCM will insert MTP or xcoder for this call but as I said I was surprised that no MTP was inserted and media goes directly between CUBE and IVR and prompts were working without any issues.

Thats reason why I asking here because its something unclear for me. If you have some IVR 11.6 you can try it and I think that you will see the same behaviour :-)

T

[cukouncukoun]

Any update regarding this??it will be good if someone from cisco could answer my questions about this :)

[cukouncukoun]

Any update regarding this??it will be good if someone from cisco could answer my questions about this :)

T