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Re: [Linphone-users] Fixed it, Praise GOD!!!!

From: Simon Morlat
Subject: Re: [Linphone-users] Fixed it, Praise GOD!!!!
Date: Mon, 12 Dec 2005 11:16:25 +0100
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About the two different ways to send digit sounds:

- with voice over ip, the recommended way is to use RFC2833: digits sounds are 
specified by their number in special RTP packets. This saves bandwidth and 
makes encoding/decoding much easier and reliable. 

- with analog telephony digits sounds are transmitted through the line as you 
hear them: a sum of two sines with normalized frequencies. This way is not 
recommended with voice over ip, because most voice over ip codec aren't able 
to reliabily encode and decode such tones (there are designed for voice, not 
for synthetic sounds).

However in order to provide to the user analog-like feeling, when you press a 
digit on linphone, you hear the tone, but the sound is not transmitted to the 
remote phone, only the RFC2833 information, which makes the remote phone to 
eventually generate the corresponding tone to the sound card (which linphone 


Le Mercredi 7 Décembre 2005 22:08, Doug Smith a écrit :
> Simon, and friends:
> That fixed it.  I was able to get into the server to set up my voice
> mail, which I am going to need for work.  I did it by pressing one
> digit at the time and enter after each one.
> Now, I have a technical question, and I really appologize, I don't
> have the time at this moment to look it up, but how does linphone, or,
> in my case, linphonec generate those tone sounds, and what is meant by
> the two different ways you said that they could be sent.
> I realize that the compression method used would mangle the sounds in
> one case, but not the other.
> Thank you.

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