[Speex-dev] Signaling tones in Speex

[Mainak Chakraborty]

Hi Jean,
Thats great news for me to start off with as I was planning to go with 16
Kbps ADPCM keeping in mind the issues and options I had. Now, whether the
additional computation cost is worth the significant bandwidth savings, I
have to see.
Just wondering if it is possible to extend this logic to G3 and G4 fax as
well, i.e. using a higher bit-rate and complexity mode for modem or fax
instead of going for a higher bit-rate ADPCM.
If so, a one stop solution for all kinds of traffic would be awesome.
Thanks a lot for the prompt reply,
Mainak

On 5/4/07, Jean-Marc Valin <jean-marc.valin at usherbrooke.ca> wrote:
>
> 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).
>
>        Jean-Marc
>
> 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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