[Freeswitch-users] Any experience with DTMF from FreeSwitch to Sonus with Vega ATAs?

[Steve Underwood]

Hi Yehavi,

Section 3.2 of RFC2833 is poorly worded, and causes a lot of issues in 
the real world. The first paragraph says you can choose to send both 
audio and events, but doesn't clarify how. Presumably RFC2198 should be 
used. Is your system using RFC2198 encoding? I doubt it. The second 
paragraph talks about tone onset getting through as audio. Valid DTMF 
can be as short as 45ms, so 60ms is far more than anything which might 
be termed onset. Because they didn't specify anything about what is 
tolerable as tone onset passing through the channel as audio we have 
chaos today.

RFC2833 is an obsolete spec, and we should be talking about RFC4733 
today. Section 2.5.1.3.1 of RFC4733 does clearly call for combined 
payloads to be sent as RFC2198 packets. RFC4733 is even vaguer about the 
onset issue, though.

Steve


On 02/20/2011 06:33 PM, Yehavi Bourvine wrote:
> Hello Steve,
>  I uderstand from paragraph 3.2 in RFC-2833 that the sender may send 
> some audio of the DTMF while sending the events, until it revognises 
> that this is a DTMF tone. The 60mSec is what I've been told by Vega 
> engineers.
>                                Thanks! __Yehavi:
>
> 2011/2/20 Steve Underwood <steveu at coppice.org <mailto:steveu at coppice.org>>
>
>     On 02/20/2011 03:31 PM, Yehavi Bourvine wrote:
>     > Hello,
>     >   Anyone has an experience with the above configuration? All
>     sides are
>     > marked as RFC-2833 and the Sonus recognises most of the DTMF's
>     twice.
>     > The Vega sends both RFC-2833 events and about 60msec of the DTMF
>     tone
>     > (according to Vega's engineers it takes it about 60 msec to
>     detect the
>     > DTMF tones).
>     > According to the RFC this is acceptable. The service provider I am
>     > working with says that it shouldn't be like that. Before I waste
>     time
>     > in wars, has anybody had this issue and knows whether it is a matter
>     > of configuration at the Sonus side?
>     >                                    Thanks! __Yehavi:
>     Are you saying the Vega sends 60ms of DTMF as audio, then sends
>     RFC2833
>     DTMF packets and mutes the audio? In what reading of the RFC is that
>     considered appropriate action? In addition, a DTMF detector should
>     detect is more like 40ms. 60ms is rather long.
>
>     Steve
>
>
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