[Freeswitch-users] Better results from mod_vmd

[Matthew Fong]

I changed

/*! Minimum time for a beep. */
#define MIN_TIME 8000
to 6500 and it seemed to work, but I'm not sure how many false positives I
will get in a real-world environment. at 4000 it fired the event like 5
times in a session, but 6500 only once. Do you think I should expect a lot
of false positives after changing this value?

--matt
http://www.hellohunter.com

On Thu, Aug 20, 2009 at 4:54 PM, Eric des Courtis <
eric.des.courtis at gmail.com> wrote:

> Matt,
>
> As is mod_vmd will not detect tones shorter then 138ms. However I
> could get that value down to ~30ms at best by making a few
> modifications to the algorithm.
>
> Cheers.
>
> Eric des Courtis
>
>
> On Thu, Aug 20, 2009 at 7:51 PM, Eric des
> Courtis<eric.des.courtis at gmail.com> wrote:
>  > Matt,
> >
> > For your information the tones you gave me are exactly 738Hz. If you
> > want to try that tone detection thing.
> >
> > Cheers.
> >
> > Eric des Courtis
> >
> > On Thu, Aug 20, 2009 at 2:20 PM, Michael Collins<msc at freeswitch.org>
> wrote:
> >>
> >>
> >> On Thu, Aug 20, 2009 at 11:06 AM, Steve Underwood <steveu at coppice.org>
> >> wrote:
> >>>
> >>> On 08/20/2009 05:22 AM, Michael Collins wrote:
> >>> >
> >>> >     There is no noise on those 3 beeps. In fact, for something that's
> >>> > been
> >>> >     through ulaw/alaw compression those beeps are very clean. They
> are
> >>> >     quite
> >>> >     short, though.
> >>> >
> >>> >
> >>> > Heck yeah they're short! Steve, in your experience is there a
> >>> > practical way to detect a beep that short without chewing up system
> >>> > resources or having lots of false positives?
> >>> > -MC
> >>> >
> >>> The tone samples I just looked at are about 130ms long. The problem is
> >>> the detector is trying to be a very open ended detector of anything
> >>> narrowband enough to be a single tone, and of any duration beyond some
> >>> small minimum. Its difficult to make such a thing voice immune unless
> >>> you can also count on a very large signal to noise ratio. With a
> digital
> >>> trunk you can probably rely on a large SNR, but what happens when
> people
> >>> use analogue lines? There is a reason why DTMF detectors try hard to
> >>> work down to about 10dB SNR. :-)
> >>>
> >>> Steve
> >>
> >> Thanks for the lesson uncle Steve! I'm guessing that the OP will need a
> new
> >> strategy. Possibly waiting for silence? Not sure what's the best way to
> go
> >> but I'm interested in hearing if someone has a solution.
> >>
> >> -MC
> >>
> >>
> >>
> >> _______________________________________________
> >> FreeSWITCH-users mailing list
> >> FreeSWITCH-users at lists.freeswitch.org
> >> http://lists.freeswitch.org/mailman/listinfo/freeswitch-users
> >> UNSUBSCRIBE:
> http://lists.freeswitch.org/mailman/options/freeswitch-users
> >> http://www.freeswitch.org
> >>
> >>
> >
>
> _______________________________________________
> FreeSWITCH-users mailing list
> FreeSWITCH-users at lists.freeswitch.org
> http://lists.freeswitch.org/mailman/listinfo/freeswitch-users
> UNSUBSCRIBE:http://lists.freeswitch.org/mailman/options/freeswitch-users
> http://www.freeswitch.org
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.freeswitch.org/pipermail/freeswitch-users/attachments/20090820/9cca7a55/attachment-0002.html