[Speex-dev] Signaling tones in Speex

Jean-Marc Valin jean-marc.valin at usherbrooke.ca
Sun May 6 23:05:37 PDT 2007

Mainak Chakraborty wrote:
> 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.

Not sure what these faxes are. It depends on how sophisticated they are.
In any case, I'm pretty sure that regardless of the test, Speex will
come up way ahead of ADPCM at any of the bit-rates it supports. BTW,
if/when you test Speex on DTMF and fax, please post the results here as
I'd be quite curious to see how it performs.



> Thanks a lot for the prompt reply,
> Mainak
> On 5/4/07, *Jean-Marc Valin* <jean-marc.valin at usherbrooke.ca
> <mailto: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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