[Freeswitch-users] Better results from mod_vmd

Eric des Courtis eric.des.courtis at gmail.com
Mon Aug 17 10:29:30 PDT 2009


You must first capture the audio beeps and verify that they are sine
waves. If not, simply tweaking the algorithm will not give you better

It might be possible to use FFT and I would be happy to help you
implement such a solution but keep in mind FFT is very very demanding
on the hardware. Ideally what you want to find out is what functions
was use to generate the beep in the first place so that it can be
detected. Is it two sines waves like in DTMF? Or something more

Anyway my email is eric.des.courtis at benbria.ca.


Eric des Courtis

On Mon, Aug 17, 2009 at 12:26 AM, Matthew Fong<mattdfong at gmail.com> wrote:
> I tried emailed Eric, seeking advice on this, but his email (the one in the
> source code) is bouncing email (invalid user), so thought I would ask here
> instead. If anyone has eric's new email address, I'd be interesting in it.
> I did some tests with mod_vmd this afternoon, but I'm only finding about 33%
> of the voice mail beeps and did have 1 false-positive in my test of 7 voice
> mail machines. I've recorded the audio of the session in .wav files that
> were both successful and not, as a comparison. I can upload the .wav files
> if they would be useful.
> mod_vmd works great for voicemails of Skype Users, and kall8.com, but has
> issues dealing with mobile phone carriers.
> sprint - not successful
> tmobile - not successful
> verizon - not successful
> panasonic home answering machine system - not successful
> kall8 - SUCCESS
> skype - SUCCESS
> I'm wondering if you can recommend a simple fix, like changing some of the
> constants like MAX_FREQ, or MIN_TIME at the top of the mod_vmd.c source
> file, or if better success requires more complex analysis.  Do you have any
> recommendations on how this might be done? Listening to the .wav's
> its apparent the beeps are not as loud for the mobile phone carriers as they
> are with skype and kall8. Any guidance would be greatly appreciated.
> --matt
> hello hunter
> http://www.hellohunter.com
> voice broadcasting & hosted dialer
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