[Linphone-developers] Wait between DTMF tones in linphonec

[Guillermo Rodriguez Garcia]

Hello all,

I am writing an application that uses linphone and needs to send DTMF codes
to operate a remote device. While looking at linphonec, I noticed that a 
pause of 1 second is inserted between tones (console/commands.c, function
linphonec_parse_command_line).

This makes the sending of DTMF codes very slow, especially when the sequence
contains several digits. Since the tones are not actually being transmitted
as audio, I thought that the pause could be removed / shortened. However when
I tried this, the other end had problems detecting the DTMF codes. This
happened both with RFC2833 and with SIP INFO. I also verified that the same
problem occurs when both ends are running linphone.

Can someone explain why is this pause needed, and why does it need to be one
second? I could not find any reason for this, specially if SIP INFO is used.

Thanks a lot,

G Rodriguez