[Asterisk-Users] DTMF inband detection improvement

[Florian Lefeuvre]

>
>
>On Feb 16, 2005, at 10:34 AM, Steve Underwood wrote:
>
>  
>
>>>>>
>>>>> BTW, Steve, if you're still reading, what is the RADIO_RELAX option 
>>>>> intended to be for in dsp.c?
>>>      
>>>
>>>
>>> It is something someone else added to the code to make the detection 
>>> criteria in relaxed mode even more relaxed. If setting that helps, 
>>> something in your channel must be causing some serious filtering of 
>>> low frequencies. Can you try logging the audio to a file, and send it 
>>> to me for analysis? chan_spy, or something like that, should do the 
>>> job.
>>>
>>    
>>
>
>Actually, it was Florian that posted about this option. I haven't tried 
>it (spent an awful lot of time last week compiling different 
>configurations of stable, head, patches...taking a break this week). 
>This is Florian said:
>
>On Feb 15, 2005, at 1:12 PM, Florian Lefeuvre wrote:
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>  
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>>>
>>> I find the compilation option RADIO_RELAX.
>>> this option change a threshold in DTMF detection (function dtmf_detect 
>>> in dsp.c)
>>> I remark an big improvement in the detection of the dtmf over GSM.
>>> have you ever test this option?
>>> RADIO is obscur for me, does it mean all wireless device?
>>>
>>> Florian
>>    
>>
>
>-mark
>

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
.