[Freeswitch-dev] libteletone multi tone detection usage

Moises Silva moises.silva at gmail.com
Sun Mar 23 04:29:40 EDT 2008


I have been working in a MFC/R2 signaling library that eventually
could be used in FreeSwitch, the library is working pretty well for
the R2 México variant and it should be easy to add new protocol
variants. I am just missing the handling of some tones (congestion,
busy, call free of charge) but that will be coming soon. During my
testing I have been using spandsp to detect and generate the required
15 MF signals. As  you may know, spandsp is GPL and not something I
plan to depend on. I want to move from spandsp to libteletone.

As a first step I created a small test case thatn generates forward MF
tones with spandsp and then try to detect them using both spandsp and
libteletone to compare results. The test case is very simple (100
lines), its source code can be found here:

If you run the test case you will see that spandsp can detect all of
the 15 MF tones using just 320 samples for each one, however,
libteletone, apparently (probably because I am not using it properly)
can only detect 9 tones using different large amount of samples (4480,
3520 etc), the remaining 6 tones are not detected at all even after
reaching the 8000 samples limit I specified.

Can somebody advice about what could be possibly wrong in how I use
libteletone to detect MF signals in the test case? Any hints will be

Kind Regards,

Moisés Silva

"I do not agree with what you have to say, but I'll defend to the
death your right to say it." Voltaire

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