[Asterisk-Users] DTMF inband detection improvement

[Steve Underwood]

Florian Lefeuvre wrote:

> Hi Steve,
>
> I was the one who post a question about the RADIO_RELAX option.
> In fact when I set it , I remark some better result in the detection 
> of the DTMF...
> after a few more tests, It appears I was wrong.
> I did a record of samples used by the DTMF_detect function.
> I obtain an audio file : PCM , 16 bits signed, big endian, Fs 8kHz.
> If I compare an audio file of DTMF  generated by land line with one 
> generated
> by GSM phone, I remarks a big difference.
> for a land line, the shape is very good., amplitude is nearly constant 
> for a dtmf.
> for a gsm phone, the shape is bad, it can can an amplitude 5 times 
> bigger than a land line.
> After some tests, I see that lot's of errors occurs when the signal 
> amplitude was too big (saturation).
> I wonder if I should clip or attenuate the signal or a better 
> detection...
> if you want I can send you some file....
>
>
> Florian

Send me some data, and I will tak a look. If the signal has overloaded 
it will not detect, as there will be too much harmonic energy to pass 
the tests.

Regards,
Steve