Matt, I think the only way to know for sure is to try it. I would try to get the value as high as possible while still detecting that 738Hz sine (with a small margin of error). Lowering the value increases false positives rapidly.
Eric des Courtis On Thu, Aug 20, 2009 at 8:36 PM, Matthew Fong<[email protected]> wrote: > 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 > <[email protected]> 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<[email protected]> 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<[email protected]> >> > wrote: >> >> >> >> >> >> On Thu, Aug 20, 2009 at 11:06 AM, Steve Underwood <[email protected]> >> >> 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 >> >> [email protected] >> >> 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 >> [email protected] >> 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 > [email protected] > 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 [email protected] http://lists.freeswitch.org/mailman/listinfo/freeswitch-users UNSUBSCRIBE:http://lists.freeswitch.org/mailman/options/freeswitch-users http://www.freeswitch.org
