[Blink] DTMF not supported

Saúl Ibarra Corretgé saul at ag-projects.com
Thu Jul 22 09:40:14 CEST 2010


On 22/07/10 00:13, Tomasz Muszynski wrote:
> Ok, I've checked again and it seems that my provider recognizes DTMF's from Blink (with and without Inband set), but with problems. I have to press digit many times to be recognized - sometimes it works quite ok, but most time it's not recognizing any digits, even after hundred of key presses (that's why I was thinking that it's not working).
> I'm not sure, but I think that DTMF signal may be to short. Is it possible to make it longer? Ideally, according to classic phones, DTMF signal should generated be as long as key is pressed.
> It's not remote problem, because from X-Lite it's working ok (it sends DTMF signals as long as key is pressed).

I did some tests myself with DTMFs being sent using RFC2833 and it did 
work. Now, we'd have to look at the tone duration you are mentioning, 
I'm currently unaware of how this is expressed as per RFC2833 (a quick 
read showed me there is a timestamp field which seems to be used for this).

In any case, I found a related bug: DTMFs (each one 200ms duration) are 
being sent continuously while you are pressing the key, while only one 
should be sent, we'll fix this.

I also experienced some DTMFs not being recognized correctly when using 
pcma and inband. This is most of the times due to network conditions, as 
data in the audio stream may not be correctly detected as a DTMF. If you 
need reliable DTMFs you should not use inband.


Saúl Ibarra Corretgé
AG Projects

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