[Asterisk-Users] dtmfmode: inband question

[Eric Wieling aka ManxPower]

Brian Buhrow wrote:
> 	Hello folks.  I'm not sure if this is the right list for this
> question, but I'll start here.
> 	If I'm using a SIP provider and I have an entry in sip.conf that looks
> like:
> 
> [8315551212]
> type => friend
> ...
> dtmfmode => inband
> ...
> 
> When I pick up the phone, call someone through this provider, and press
> numeric digits to generate dtmf tones, who is actually generating the tones
> at the other end?
> What I'm noticing is that if I call a pstn line using an entry like this
> through asterisk, and then press digits on the SIP phone connected to
> asterisk, I hear very short tones on the pstn line instead of the long
> tones I generate on the SIP phone.  In addition, if I press digits too
> quickly on the SIP phone, where "too quickly" is not very fast at all, many
> digits are dropped entirely and do not make it to the pstn phone at all.
> It occurred to me that this might be a fixable problem in the Asterisk
> source code, but when I read the code itself, it is not clear to me who is
> generating these short dtmf bursts, and perhaps it is the fault of the SIP
> instrument, a Cisco 7960 running SIP image 6.2, it self.
> 	So, if anyone can explain to me where the DTMF tones are coming from
> when the  dtmfmode is set to "inband", I'd be most appreciative.

sip.conf does not use =>, it uses =.  i.e. type=friend

With inband dtmf the device that you press the key on will generate the 
DTMF.  If the codec is ulaw or alaw the DTMF will come thru loud and 
clear.  If the codec is not ulaw or alaw then the DTMF will be corrupted 
by the audio compression and you will hear a very short sound or a 
garbled tone.  Of course if the phone is set for RFC2833 and asterisk is 
set for inband then you may not hear anything at all.

--Eric

-- 
I am seeking part or full time employment in the Greater Toronto Area, 
My preference is part time employment with some telecommuting, but all 
offers will be considered. Contact eric at fnords.org.