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<mattdfong@gmail.com> 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 <eric.des.courtis@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@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@freeswitch.org> wrote:
On Thu, Aug 20, 2009 at 11:06 AM, Steve Underwood <steveu@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@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@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@lists.freeswitch.org http://lists.freeswitch.org/mailman/listinfo/freeswitch-users UNSUBSCRIBE:http://lists.freeswitch.org/mailman/options/freeswitch-users http://www.freeswitch.org