asterisk users - Oct 2015 - DTMF talkoff beep (still)

Hi all,

 

I am still receiving reports from some users that calls they make or receive
contain loud deafening beeps that can last a couple of seconds. I understand
this is DTMF talkoff and is being triggered because the phone interprets
speech as a key press (say if someone is pressing 1 at an IVR). Asterisk
triggers DTMF emulation when the talkoff duration is less than 80ms, and I
have found a variable in channel.c that I *think* I need to change to make
it more tolerant, but it looks like I'll need to recompile the whole
platform from source for it to take effect (how would I do that given I'm
using a prepackaged FreepBX distro?)

 

We are using an FreePBX Asterisk phone system with both SIP in and SIP out
trunks for connectivity. My question is how do people running SIP phone
systems mitigate against this? I understand Asterisk SIP implementations can
be fairly prone to things such as DTMF talkoff. It's very annoying for the
end users.

 

I have tried a variety of different settings on the phones (Cisco SPA512G),
including InBand/OutBand etc, such as the following but without any success
- the users keep reporting the same problem.

 



 



 



 



 

Cisco's InBand/OutBand DTMF implementation/setting doesn't seem the
clearest
compared to other phones I've deployed.

 

As always, thoughts appreciated.

 

Regards,

 

Jamie 

 

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On 9/10/2015, at 5:16 AM, Jamie Rees <jrees at gmlnt.com> wrote:
> <snip>
> 
> I understand this is DTMF talkoff
> <snip>
> 
> My question is how do people running SIP phone systems mitigate against
this?

My personal answer to this question has been to completely avoid the use of any
ATAs at all. Since taking that approach I have never had to deal with the
problem again.

Not sure how much practical use that is to you in your own situation, but it
worked for me!

Pete

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