[Speex-dev] Signaling tones in Speex

Jean-Marc Valin jean-marc.valin at usherbrooke.ca
Fri May 4 06:19:11 PDT 2007

Hi Mainak,

Speex will definitely be able to handle DTMF. The only question is what
the minimum rate for that will be. I remember testing on a few tones at
8 kbps and I didn't hear too much distortion (though there have have
been). The only thing I can recommend is to use a higher complexity
setting that one would normally use. For voice, I can't really tell the
difference between quality 1 and quality 3, but for DTMF, it actually
makes a big difference. I'd recommend using complexity 3 or 4 if you can
afford it (in speexenc, you can change that with --comp and the default
is 3).


Mainak Chakraborty a écrit :
> Hi all,
> Has anyone tried conveying signaling tones (DTMF) through speex? If so, can
> i get an idea of the lowest bit-rate at which I can do so with 'tolerable
> distortion'. G.728 does so and G.729E (11.8 Kbps mode) is 'claimed' to
> do so
> but even if true, G.729 (rather G.729I - 11.8/8/6.4 kbps) does not allow me
> to go below 6.4 kbps if needed. Basically I am looking for a single codec
> which would allow me to play with multiple (low) bit-rates within voice and
> switch to a higher bit-rate upon detecting a signaling tone instead of
> using
> RFC 2833/out-of-band signaling methods. I hope speex is the solution am
> looking for!
> Regards,
> Mainak
> PS: In any case I will have to test it out myself but a positive answer to
> this query would definelty brighten up the road ahead :-)
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