[asterisk-users] DTMF between cisco and sipura going through asterisk

[Greg Boehnlein]

On Tue, 29 Aug 2006, Benjamin Lawetz wrote:

> Hello all,
> 
> 	we're having an issue with DTMFs being sent to Sipura's. Calls are
> originating from a Cisco AS5300 being sent to asterisk which in turn sends
> it to the Sipura. Connected to the Sipura is a legacy PBX (or actually shows
> the same problem with a cheap answering machine). The DTMFs sent from the
> AS5300 aren't recognised by the legacy PBX.
> 
> - DTMFs are recognised correctly on the asterisk (when we check voicemail)
> - The cisco is setup with dtmf-relay rtp-nte
> - in sip.conf the cisco and sipura are set to rfc2833
> 
> If I set the cisco in dtmf-relay rtp-cisco it works on the sipura, but not
> on the asterisk.
> 
> Unfortunately I can only set one dtmf-relay mode on the cisco. Is there
> anything I can change on asterisk or sipura to get the sipura to work with
> the rtp-nte (or to get asterisk to work with the cisco-rtp)?
> 
> Any hints can help,

Ben,
	What version of Aserisk are you using? If it is the 1.2 series, 
there are all sorts of RFC-2833 DTMF Relay issues that can crop up. My 
suggestion is that if you are willing to take the time, it might be worth 
it to Upgrade to the pre-release version of Asterisk that is currently in 
TRUNK. This supports the new Variable Length DTMF code that should knock 
out nearly all of the DTMF issues that Asterisk has had. The 1.2 and 
earlier RTP stack and RFC-2833 implementation, while not technically wrong 
according to the RFC, did things a bit differently than the rest of the 
world has chosen, and therefore can cause DTMF instability.

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