[pjsip] DTMF

Benny Prijono bennylp at pjsip.org
Thu Feb 21 16:50:13 EST 2008

On 2/21/08, Norman Franke <norman at myasd.com> wrote:
> Although, in my experience using a tonegen often results in tones that are
> not understood by a number of other systems. I'm not sure if this is due to
> audio volume issues or what, but we've had a number of systems that can't
> understand some or all digits from the tonegen. Sending SIP INFO messages to
> our Cisco to then generate them always works.

The tone generator heavily depends on the quality of sine wave
generation, and in PJMEDIA, I use a sine wave emulation which I
thought should give good balance between quality and speed. With this
method, speed definitely is much better than using math.h, but
quality, well turns out not to be perfect. I'm aware that the longer
the tone is, the more deviation it'll have from the perfect tone.

Have a look at tonegen.c for more info. Thanks for the feedback though.


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