[asterisk-biz] Solving DTMF issue

[Trixter aka Bret McDanel]

dtmf in asterisk (rfc2833) violates the rfc.  There are many switches
that usually are only "big carrier types" that do not properly deal with
what asterisk sends.  I gave oej specifics as he was doing something
relating to a filed bug on this issue.  I even wrote a patch, but until
asterisk is no longer released gpl I cant contribute it (personal thing
just as some wont contribute unless its gpl I wont contribute if it is).

So what you should have said is the simpliest solution is to use a
provider that does not require rfc compliant dtmf, or uses a gateway
that will redo the RTP flow to make it compliant.

As for the original poster, there are 3 main methods for dtmf, auto
tries to select the best one.  There is sip-info which dtmf is sent as
sip messages - you cant guarantee they are arrived in order unless you
have a tcp connection which asterisk violates the sip rfc by not having
tcp support (its not optional, its required).

There is inband which is what the pstn uses, and it only works well with
some codecs, with voip when there is low jitter and loss, and requires
more cpu to process (each frame it has to look and see if there is
dtmf).

There is also rfc2833 (now "deprecated" by rfc4733, yeah adding 1900
fixed y2k why wont it fix a poorly worded rfc?!).  This is sent in the
RTP stream and with SIP negotiated via the SDP.  

You said that the provider sends "several dtmf mode" to your server,
what does that mean?  In the SDP there are multiple entries for rfc2833
(required if you support more thna one sample rate, and likely to break
most devices, sigh) or what?  


On Wed, 2008-04-02 at 11:14 -0800, John van Oppen wrote:
> The simplest solution is to just use a provider that implements this
> properly.   I know our providers (big international networks) all
> support this with no problem, if you are seeing many different types of
> DTMF you likely have a very broken reseller in the path...


> On Behalf Of Cyriaz at Gmail.com

> I would like to hire an expert who can absolutely fix the following
> issue:
> 
> I have SIP providers who sends several DTMF mode to my asterisk at
> different times. We have changed "dtmfmode=auto" and still sometimes
> it recognized dtmf and sometimes not. I need someone to identify the
> issue and detect all DTMF mode sent by the SIP provider no matter what
> it is and pass it to asterisk without any problem.
> 
> Thanks

-- 
Trixter http://www.0xdecafbad.com     Bret McDanel
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