[asterisk-dev] DTMF detection and generation code

[Vahan Yerkanian]

Eric "ManxPower" Wieling wrote:
> If this is the case then these applications will not work for calls from 
> a cell phone.  These applications also will not work for calls from many 
> larger PBXs.  I think Steve's problem is that he does not believe that 
> anyone would write applications in such a way that they will not work 
> with calls from cell phones.  I agree with him.

Eric,

What I meant was that currently Asterisk's DTMF duration is quite short, 
if I'm not mistaken it's 800 samples or 100ms, and sometimes it gets too 
mangled due to jitter or lost packets to be successfully detected.

Increasing the number of the redundant outband dtmf packets sent 
increases the chance of receiving a sufficient amount of them to be able 
to reconstruct the DTMF tone. As Asterisk is used all over the world 
with different phone line qualities etc, it is worth making a 
configurable option for the this.

On the same time, if Asterisk replaces an existing PBX, customers might 
have previous habits/experience on how long they have to press the 
keypad buttons for their bank's IVR and how long for a home answering 
machine's pin. Those durations might differ - hence the need of DTMF 
duration accuracy.

Vahan